Method for reporting channel state information, user equipment, and base station

ABSTRACT

Embodiments of the present invention provide a method includes: receiving a reference signal sent by a base station; selecting, based on the reference signal, a precoding matrix from a codebook, where a precoding matrix W included in the codebook is a product of three matrices being W 1 , Z, and W 2 , that is, w=w 1 zw 2 , where both W 1  and Z are block diagonal matrices, W 1 =a formula (I), Z=a formula (II), each of W 1  and Z includes at least one block matrix, that is, N B ≥1, and each column of each block matrix Z i  in the matrix Z has the following structure formula (III); and sending a precoding matrix indicator (PMI) to the base station, where the PMI corresponds to the selected precoding matrix, and is used by the base station to obtain the selected precoding matrix W according to the PMI.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/808,318, filed on Nov. 9, 2017, now issued as U.S. Pat. No.10,063,296 issued on Aug. 28, 2018, which is a continuation of U.S.patent application Ser. No. 15/439,686, filed on Feb. 22, 2017, now U.S.Pat. No. 9,838,097, which is a continuation of U.S. patent applicationSer. No. 14/883,334, filed on Oct. 14, 2015, now U.S. Pat. No.9,608,708, which is a continuation of International Application No.PCT/CN2013/074214, filed on Apr. 15, 2013. All of the afore-mentionedpatent applications are hereby incorporated by reference in theirentireties.

TECHNICAL FIELD

The present invention relates to the field of communicationstechnologies, and in particular, to a method for reporting channel stateinformation, user equipment, and a base station.

BACKGROUND

In a multiple input multiple output (MIMO) system, to eliminateco-channel interference caused by multiple users and multiple antennas,some necessary signal processing technologies need to be used at twoends of a transceiver, so as to improve communication performance of thesystem.

In the prior art, a precoding technology is proposed, and a majorprinciple of the precoding technology is that a base station uses knownchannel state information (CSI) to design a precoding matrix forprocessing a sent signal, so as to reduce interference on the sentsignal. A MIMO system using precoding may be represented as follows:y=HVs+n

where y is a received signal vector, H is a channel matrix, V is aprecoding matrix, s is a transmitted symbol vector, and n is aninterference and noise vector.

Optimal precoding usually requires that a transmitter entirely knowschannel state information (CSI). In a common method, a terminalquantizes instantaneous CSI and feeds back the instantaneous CSI to abase station (BS).

In an existing long term evolution (LTE) R8 system, CSI information fedback by a terminal includes information such as a rank indicator (RI), aprecoding matrix indicator (PMI), and a channel quality indicator (CQI),where the RI and the PMI respectively indicate a used layer quantity anda used precoding matrix. A set of used precoding matrices is generallyreferred to as a codebook, where each precoding matrix is a code word inthe codebook. An existing LTE R8 4-antenna codebook is designed based ona Householder transformation, and a code word of the codebook may becompatible with a uniform linear array antenna configuration and a crosspolarization antenna configuration. Double-codebook design for 8antennas is introduced in an LIE R10 system, and quantization accuracyis further improved without excessively increasing feedback overheads.

On one hand, the foregoing LTE R8 to R10 codebooks are mainly designedfor a macro cell system. A position of a base station or a transmitteris usually higher than the height of a surrounding building (forexample, the height of an antenna is approximately between 200 to 250feet); therefore, a major transmission path of the base station or thetransmitter is higher than a roof, and a transmitted multipath componentusually surrounds a direction of a line of sight (Line of Sight, LOS forshort). In this way, each multipath component is usually located withina plane in which the line of sight is located, that is, angle extensionin a pitch angle direction approaches 0. On the other hand, theforegoing codebooks are designed based on a conventional base stationantenna; for the conventional base station antenna, a perpendicularantenna beam having a fixed tilt angle is used, but only a direction ofa horizontal beam can be adjusted dynamically.

However, to conform to user density and a data service demand that areincreasing rapidly, and to further reduce transmit power, the concept ofmicro cell is further introduced. A position of a base station or atransmitter in a micro cell system is usually lower than the height of asurrounding building (for example, an antenna is installed on a lamppostin a street, and usually is at a height of approximately 30 feet), and awireless transmission mechanism of the micro cell system is obviouslydifferent from the foregoing macro cell environment, where somemultipath components may surround a LOS direction, and some othermultipath components are probably along the ground or the street. Thisdouble-transmission mechanism causes larger angle extension, especiallyin a direction of a pitch angle, which is obviously different from themacro cell. Currently, design of LTE R8-R10 codebooks cannot be welladapted to the foregoing micro cell environment.

In addition, to further improve spectrum efficiency, currently, in anLTE R12 standard to be launched, introduction of more antennaconfigurations, especially an antenna configuration based on an activeantenna system (AAS), starts to be considered. Different from aconventional base station, an AAS base station further provides freedomin designing an antenna in a perpendicular direction, which is mainlyimplemented by using a two-dimensional antenna array in horizontal andperpendicular directions of the antenna; the conventional base stationactually uses a horizontal one-dimensional array, although each antennaport in a horizontal direction of the antenna may be obtained byperforming weighting on multiple array elements in a perpendiculardirection. Currently, the design of the LTE R8-R10 codebooks cannot bewell adapted to the foregoing antenna configuration.

SUMMARY

Embodiments of the present invention provide a method for reportingchannel state information, user equipment, and a base station. In aprecoding matrix indicated in the channel state information reported bythe user equipment, a channel characteristic of a double-transmissioncondition in a micro cell network environment and freedom in horizontaland perpendicular directions of an antenna of an AAS base station areconsidered, which can improve communication performance of the microcell network environment and an AAS base station system.

To achieve the foregoing objective, the following technical solutionsare used in the embodiments of the present invention:

According to a first aspect, an embodiment of the present inventionprovides a method for reporting channel state information, where themethod includes:

receiving a reference signal sent by a base station;

selecting, based on the reference signal, a precoding matrix from acodebook, where a precoding matrix w included in the codebook is aproduct of three matrices being W₁, z, and W₂, that is, W=W₁ZW₂, where

both W₁ and Z are block diagonal matrices, W₁=diag{X₁, . . . , X_(N)_(B) }, Z=diag{Z₁, . . . , Z_(N) _(B) }, each of W₁ and Z includes atleast one block matrix, that is, N_(B)≥1, and each column of each blockmatrix Z_(i) in the matrix z has the following structure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T)

where [ ]^(T) represents matrix transposition; e_(i,k) represents ann_(i)x1 selection vector, where in the vector, the k^(th) element is 1and all other elements are 0, and n_(i) is a half of a column quantityof a block matrix x_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, andβ_(i,k)≥0; and

sending a precoding matrix indicator PMI to the base station, where thePMI corresponds to the selected precoding matrix, and is used by thebase station to obtain the selected precoding matrix W according to thePMI.

In a first possible implementation manner, with reference to the firstaspect, the selecting, based on the reference signal, a precoding matrixfrom a codebook specifically includes:

selecting, based on the reference signal, the precoding matrix from acodebook subset, where the codebook subset is a subset predefined, ornotified by the base station, or reported by user equipment.

In a second possible implementation manner, with reference to the firstpossible implementation manner, the codebook subsets share at least onesame matrix subset of the following matrix subsets: subsets of a matrixW₁, a matrix W₁Z, a matrix W₂, a matrix ZW₂, and a matrix Z.

In a third possible implementation manner, with reference to the firstaspect or the first and second possible implementation manners, thesending a precoding matrix indicator PMI to the base stationspecifically includes:

sending a first precoding matrix indicator PMI₁ and a second precodingmatrix indicator PMI₂ to the base station, where the PMI₁ is used toindicate the matrix W₁Z, and the PMI₂ is used to indicate the matrix W₂;or

sending a third precoding matrix indicator PMI₃ and a fourth precodingmatrix indicator PMI₄ to the base station, where the PMI₃ is used toindicate the matrix W₁, and the PMI₄ is used to indicate the matrix ZW₂;or

sending a second precoding matrix indicator PMI₂, a third precodingmatrix indicator PMI₃, and a fifth precoding matrix indicator PMI₅ tothe base station, where the PMI5 is used to indicate the matrix z.

In a fourth possible implementation manner, with reference to the thirdpossible implementation manner, the sending a precoding matrix indicatorPMI to the base station specifically includes:

sending the PMI₁ to the base station according to a first period; and

sending the PMI₂ to the base station according to a second period, wherethe first period is greater than the second period; or

sending the PMI₃ to the base station according to a third period; and

sending the PMI₄ to the base station according to a fourth period, wherethe third period is greater than the fourth period; or

sending the PMI₂ to the base station according to a second period;

sending the PMI₃ to the base station according to a third period; and

sending the PMI₅ to the base station according to a fifth period, wherethe third period is less than the second period and the fifth period.

In a fifth possible implementation manner, with reference to the thirdpossible implementation manner, the sending a precoding matrix indicatorPMI to the base station specifically includes:

sending the PMI₁ to the base station according to a first frequencydomain granularity; and

sending the PMI₂ to the base station according to a second frequencydomain granularity, where the first frequency domain granularity isgreater than the second frequency domain granularity; or

sending the PMI₃ to the base station according to a third frequencydomain granularity; and

sending the PMI₄ to the base station according to a fourth frequencydomain granularity, where the third frequency domain granularity isgreater than the fourth frequency domain granularity; or

sending the PMI₂ to the base station according to a second frequencydomain granularity;

sending the PMI₃ to the base station according to a third frequencydomain granularity; and

sending the PMI₅ to the base station according to a fifth frequencydomain granularity, where the third frequency domain granularity is lessthan the second frequency domain granularity and the fifth frequencydomain granularity.

In a sixth possible implementation manner, with reference to the firstaspect or the first to fifth possible implementation manners, the blockmatrix X_(i)=[X_(i,1) X_(i,2)], where each column of the matrix X_(i,j)is selected from columns of a Householder matrix, a discrete Fouriertransform matrix, a Hadamard matrix, a rotated Hadamard matrix, or aprecoding matrix in an LTE R8 system 2-antenna or 4-antenna codebook orin an LTE R10 system 8-antenna codebook.

In a seventh possible implementation manner, with reference to the sixthpossible implementation manner, each column of the matrix X_(i,j), j=1,2 is separately selected from columns of different Householder matrices,different discrete Fourier transform matrices, different Hadamardmatrices, different rotated Hadamard matrices, or different precodingmatrices in an LTE R8 system 2-antenna or 4-antenna codebook or in anLTE R10 system 8-antenna codebook.

In an eighth possible implementation manner, with reference to the firstaspect or the first to fifth possible implementation manners, the blockmatrix X_(i)=[X_(i,1) X_(i,2)], where the matrix X_(i,j) is a Kroneckerproduct of two matrices being A_(i,j) and B_(i,j), and j=1, 2.

In a ninth possible implementation manner, with reference to the eighthpossible implementation manner, columns of the matrix X_(i,1) and thematrix X_(i,2) are column vectors of a Householder matrix, a DFT matrix,a Hadamard matrix, a rotated Hadamard matrix, or a precoding matrix inan LTE R8 system 2-antenna or 4-antenna codebook or in an LTE R10 system8-antenna codebook.

In a tenth possible implementation manner, with reference to the firstaspect or the first to ninth possible implementation manners, W₁ is anidentity matrix.

In an eleventh possible implementation manner, with reference to thefirst aspect or the first to tenth possible implementation manners, acolumn vector in the matrix W₂ has a structure y_(n)=γ⁻¹[e_(n) ^(T)e^(jθ) ^(n) e_(n) ^(T)]^(T), where e_(n) represents a selection vector;where in the vector, the n^(th) element is 1 and all other elements are0; θ_(n) is a phase shift; and γ is a positive constant.

According to a second aspect, an embodiment of the present inventionprovides a method for reporting channel state information, where themethod includes:

sending a reference signal to user equipment UE;

receiving a precoding matrix indicator PMI sent by the UE; and

determining a precoding matrix w in a codebook according to the PMI,where the precoding matrix w is a product of three matrices being W₁, z,and W₂ that is, W=W₁ZW₂, where

both w_(i) and z are block diagonal matrices, W₁=diag{X₁, . . . , X_(N)_(B) }, Z=diag{Z₁, . . . , Z_(N) _(B) }, each of W₁ and z includes atleast one block matrix, that is, N_(B)≥1, and each column of each blockmatrix Z_(i) in the matrix z has the following structure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T)

where [ ]^(T) represents matrix transposition; e_(i,k) represents ann_(i)x1 selection vector, where in the vector, the k^(th) element is 1and all other elements are 0, and n_(i) is a half of a column quantityof a block matrix x_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, andβ_(i,k)≥0.

In a first possible implementation manner, with reference to the secondaspect, the determining a precoding matrix w in a codebook according tothe PMI specifically includes:

determining the precoding matrix in a codebook subset according to thePMI, where the codebook subset is a subset predefined, or reported bythe user equipment, or notified by a base station.

In a second possible implementation manner, with reference to the firstpossible implementation manner, the codebook subsets share at least onesame matrix subset of the following matrix subsets: subsets of a matrixW₁, a matrix W₁Z, a matrix W₂, a matrix ZW₂, and a matrix z.

In a third possible implementation manner, with reference to the secondaspect or the first and second possible implementation manners, thereceiving a precoding matrix indicator PMI sent by the UE specificallyincludes:

receiving a first precoding matrix indicator PMI₁ and a second precodingmatrix indicator PMI₂ that are sent by the UE, where the PMI₁ is used toindicate the matrix W₁Z, and the PMI₂ is used to indicate the matrix W₂;

or

receiving a third precoding matrix indicator PMI₃ and a fourth precodingmatrix indicator PMI₄ that are sent by the UE, where the PMI₃ is used toindicate the matrix W₁, and the PMI₄ is used to indicate the matrix ZW₂;

or

receiving a second precoding matrix indicator PMI₂, a third precodingmatrix indicator PMI₃, and a fifth precoding matrix indicator PMI₅ thatare sent by the UE, where the PMI5 is used to indicate the matrix z.

In a fourth possible implementation manner, with reference to the thirdpossible implementation manner, the receiving a precoding matrixindicator PMI sent by the UE specifically includes:

receiving, according to a first period, the PMI₁ sent by the UE; and

receiving, according to a second period, the PMI₂ sent by the UE, wherethe first period is greater than the second period; or

receiving, according to a third period, the PMI₃ sent by the UE; and

receiving, according to a fourth period, the PMI₄ sent by the UE, wherethe third period is greater than the fourth period; or

receiving, according to a second period, the PMI₂ sent by the UE;

receiving, according to a third period, the PMI₃ sent by the UE; and

receiving, according to a fifth period, the PMI₅ sent by the UE, wherethe third period is less than the second period and the fifth period.

In a fifth possible implementation manner, with reference to the thirdpossible implementation manner, the receiving a precoding matrixindicator PMI sent by the UE specifically includes:

receiving, according to a first frequency domain granularity, the PMI₁sent by the UE; and

receiving, according to a second frequency domain granularity, the PMI₂sent by the UE, where the first frequency domain granularity is greaterthan the second frequency domain granularity; or

receiving, according to a third frequency domain granularity, the PMI₃sent by the UE; and

receiving, according to a fourth frequency domain granularity, the PMI₄sent by the UE, where the third frequency domain granularity is greaterthan the fourth frequency domain granularity; or

receiving, according to a second frequency domain granularity, the PMI₂sent by the UE;

receiving, according to a third frequency domain granularity, the PMI₃sent by the UE; and

receiving, according to a fifth frequency domain granularity, the PMI₅sent by the UE, where the third frequency domain granularity is lessthan the second frequency domain granularity and the fifth frequencydomain granularity.

In a sixth possible implementation manner, with reference to the secondaspect or the first to fifth possible implementation manners, the blockmatrix X_(i)=[X_(i,1) X_(i,2)], where each column of the matrix X_(i,j)is selected from columns of a Householder matrix, a discrete Fouriertransform matrix, a Hadamard matrix, a rotated Hadamard matrix, or aprecoding matrix in an LTE R8 system 2-antenna or 4-antenna codebook orin an LTE R10 system 8-antenna codebook.

In a seventh possible implementation manner, with reference to the sixthpossible implementation manner, each column of the matrix X_(i,j), j=1,2 is separately selected from columns of different Householder matrices,different discrete Fourier transform matrices, different Hadamardmatrices, different rotated Hadamard matrices, or different precodingmatrices in an LTE R8 system 2-antenna or 4-antenna codebook or in anLTE R10 system 8-antenna codebook.

In an eighth possible implementation manner, with reference to thesecond aspect or the first to fifth possible implementation manners, theblock matrix X_(i)=[X_(i,1) X_(i,2)], where the matrix X_(i,j) is aKronecker product of a matrix A_(i,j) and a matrix B_(i,j), and j=1, 2.

In a ninth possible implementation manner, with reference to the eighthpossible implementation manner, columns of the matrix X_(i,1) and thematrix X_(i,2) are column vectors of a Householder matrix, a discreteFourier transform matrix, a Hadamard matrix, a rotated Hadamard matrix,or a precoding matrix in an LTE R8 system 2-antenna or 4-antennacodebook or in an LTE R10 system 8-antenna codebook.

In a tenth possible implementation manner, with reference to the secondaspect or the first to ninth possible implementation manners, W₁ is anidentity matrix.

In an eleventh possible implementation manner, with reference to thesecond aspect or the first to tenth possible implementation manners, acolumn vector in the matrix W₂ has a structure y_(n)=γ⁻¹[e_(n) ^(T)e^(jθ) ^(n) e_(n) ^(T)]^(T), where e_(n) represents a selection vector;where in the vector, the n^(th) element is 1 and all other elements are0; θ_(n) is a phase shift; and γ is a positive constant.

According to a third aspect, an embodiment of the present inventionprovides an apparatus for reporting channel state information, which maybe a user equipment or a chip, where the apparatus includes: a receiver,a processor, and a transmitter, where

the receiver is configured to receive a reference signal sent by a basestation;

the processor is configured to select, based on the reference signal, aprecoding matrix from a codebook, where a precoding matrix w included inthe codebook is a product of three matrices being W₁, Z, and W₂, thatis, W=W₁ZW₂, where

both w₁ and z are block diagonal matrices, W₁=diag{X₁, . . . , X_(N)_(B) }, Z=diag{Z₁, . . . , Z_(N) _(B) }, each of w₁ and z includes atleast one block matrix, that is, N_(B)≥1, and each column of each blockmatrix Z_(i) in the matrix z has the following structure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T)

where [ ]^(T) represents matrix transposition; e_(i,k) represents ann_(i)x1 selection vector, where in the vector, the k^(th) element is 1and all other elements are 0, and n_(i) is a half of a column quantityof a block matrix x_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, andβ_(i,k)≥0; and

the transmitter is configured to send a precoding matrix indicator PMIto the base station, where the PMI corresponds to the selected precodingmatrix, and is used by the base station to obtain the selected precodingmatrix W according to the PMI.

In a first possible implementation manner, with reference to the thirdaspect, the processor is specifically configured to select, based on thereference signal, the precoding matrix from a codebook subset, where thecodebook subset is a subset predefined, or notified by the base station,or reported by the user equipment.

In a second possible implementation manner, with reference to the firstpossible implementation manner, the codebook subsets share at least onesame matrix subset of the following matrix subsets: subsets of a matrixW₁, a matrix w₁z, a matrix W₂, a matrix zw₂, and a matrix Z.

In a third possible implementation manner, with reference to the thirdaspect or the first and second possible implementation manners, thetransmitter is specifically configured to send a first precoding matrixindicator PMI₁ and a second precoding matrix indicator PMI₂ to the basestation, where the PMI₁ is used to indicate the matrix w₁z, and the PMI₂is used to indicate the matrix W₂; or

send a third precoding matrix indicator PMI₃ and a fourth precodingmatrix indicator PMI₄ to the base station, where the PMI₃ is used toindicate the matrix w₁, and the PMI₄ is used to indicate the matrix zw₂;or

send a second precoding matrix indicator PMI₂, a third precoding matrixindicator PMI₃, and a fifth precoding matrix indicator PMI₅ to the basestation, where the PMI5 is used to indicate the matrix z.

In a fourth possible implementation manner, with reference to the thirdpossible implementation manner, the transmitter is specificallyconfigured to send the PMI₁ to the base station according to a firstperiod; and

send the PMI₂ to the base station according to a second period, wherethe first period is greater than the second period; or

send the PMI₃ to the base station according to a third period; and

send the PMI₄ to the base station according to a fourth period, wherethe third period is greater than the fourth period; or

send the PMI₂ to the base station according to a second period;

send the PMI₃ to the base station according to a third period; and

send the PMI₅ to the base station according to a fifth period, where thethird period is less than the second period and the fifth period.

In a fifth possible implementation manner, with reference to the thirdpossible implementation manner, the transmitter is specificallyconfigured to send the PMI₁ to the base station according to a firstfrequency domain granularity; and

send the PMI₂ to the base station according to a second frequency domaingranularity, where the first frequency domain granularity is greaterthan the second frequency domain granularity; or

send the PMI₃ to the base station according to a third frequency domaingranularity; and

send the PMI₄ to the base station according to a fourth frequency domaingranularity, where the third frequency domain granularity is greaterthan the fourth frequency domain granularity; or

send the PMI₂ to the base station according to a second frequency domaingranularity;

send the PMI₃ to the base station according to a third frequency domaingranularity; and

send the PMI₅ to the base station according to a fifth frequency domaingranularity, where the third frequency domain granularity is less thanthe second frequency domain granularity and the fifth frequency domaingranularity.

In a sixth possible implementation manner, with reference to the thirdaspect or the first to fifth possible implementation manners, the blockmatrix X_(i)=[X_(i,1) X_(i,2)], where each column of the matrix X_(i,j)is selected from columns of a Householder matrix, a discrete Fouriertransform matrix, a Hadamard matrix, a rotated Hadamard matrix, or aprecoding matrix in an LTE R8 system 2-antenna or 4-antenna codebook orin an LTE R10 system 8-antenna codebook.

In a seventh possible implementation manner, with reference to the sixthpossible implementation manner, each column of the matrix X_(i,j), j=1,2 is separately selected from columns of different Householder matrices,different discrete Fourier transform matrices, different Hadamardmatrices, different rotated Hadamard matrices, or different precodingmatrices in an LTE R8 system 2-antenna or 4-antenna codebook or in anLTE R10 system 8-antenna codebook.

In an eighth possible implementation manner, with reference to the thirdaspect or the first to fifth possible implementation manners, the blockmatrix X_(i)=[X_(i,1) X_(i,2)], where the matrix X_(i,j) is a Kroneckerproduct of two matrices being A_(i,j) and B_(i,j), and j=1, 2.

In a ninth possible implementation manner, with reference to the eighthpossible implementation manner, columns of the matrix X_(i,1) and thematrix X_(i,2) are column vectors of a Householder matrix, a discreteFourier transform matrix, a Hadamard matrix, a rotated Hadamard matrix,or a precoding matrix in an LTE R8 system 2-antenna or 4-antennacodebook or in an LTE R10 system 8-antenna codebook.

In a tenth possible implementation manner, with reference to the thirdaspect or the first to ninth possible implementation manners, w₁ is anidentity matrix.

In an eleventh possible implementation manner, with reference to thethird aspect or the first to tenth possible implementation manners, acolumn vector in the matrix W₂ has a structure y_(n)=γ⁻¹[e_(n) ^(T)e^(jθ) ^(n) e_(n) ^(T)]^(T), where e_(n) represents a selection vector;where in the vector, the n^(th) element is 1 and all other elements are0; θ_(n) is a phase shift; and γ is a positive constant.

According to a fourth aspect, an embodiment of the present inventionprovides an apparatus for reporting channel state information, which maybe abase station or a chip, where the apparatus includes: a transmitter,a receiver, and a processor, where

the transmitter is configured to send a reference signal to userequipment UE;

the receiver is configured to receive a precoding matrix indicator PMIsent by the UE; and

the processor is configured to determine a precoding matrix w in acodebook according to the PMI, where the precoding matrix w is a productof three matrices being W₁, z, and W₂, that is, W=W₁ZW₂, where

both w₁ and z are block diagonal matrices, W₁=Z=diag{X₁, . . . , X_(N)_(B) }, Z=diag{Z₁, . . . , Z_(N) _(B) }, each of W₁ and Z includes atleast one block matrix, that is, N_(B)≥1 and each column of each blockmatrix Z_(i) in the matrix Z has the following structure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T)

where [ ]^(T) represents matrix transposition; e_(i,k) represents ann_(i)x1 selection vector, where in the vector, the k^(th) element is 1and all other elements are 0, and n_(i) is a half of a column quantityof a block matrix x_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, andβ_(i,k)≥0.

In a first possible implementation manner, with reference to the fourthaspect, the processor is specifically configured to:

determine the precoding matrix in a codebook subset according to thePMI, where the codebook subset is a subset predefined, or reported bythe user equipment, or notified by the base station.

In a second possible implementation manner, with reference to the firstpossible implementation manner, the codebook subsets share at least onesame matrix subset of the following matrix subsets: subsets of a matrixW₁, a matrix W₁Z, matrix W₂, a matrix ZW₂, and a matrix z.

In a third possible implementation manner, with reference to the fourthaspect or the first and second possible implementation manners, thereceiver is specifically configured to:

receive a first precoding matrix indicator PMI₁ and a second precodingmatrix indicator PMI₂ that are sent by the UE, where the PMI₁ is used toindicate the matrix W₁Z, and the PMI₂ is used to indicate the matrix W₂;

or

receive a third precoding matrix indicator PMI₃ and a fourth precodingmatrix indicator PMI₄ that are sent by the UE, where the PMI₃ is used toindicate the matrix W₁, and the PMI₄ is used to indicate the matrix ZW₂;

or

receive a second precoding matrix indicator PMI₂, a third precodingmatrix indicator PMI₃, and a fifth precoding matrix indicator PMI₅ thatare sent by the UE, where the PMI5 is used to indicate the matrix z.

In a fourth possible implementation manner, with reference to the thirdpossible implementation manner, the receiver is specifically configuredto:

receive, according to a first period, the PMI₁ sent by the UE; and

receive, according to a second period, the PMI₂ sent by the UE, wherethe first period is greater than the second period; or

receive, according to a third period, the PMI₃ sent by the UE; and

receive, according to a fourth period, the PMI₄ sent by the UE, wherethe third period is greater than the fourth period; or

receive, according to a second period, the PMI₂ sent by the UE;

receive, according to a third period, the PMI₃ sent by the UE; and

receive, according to a fifth period, the PMI₄ sent by the UE, where thethird period is less than the second period and the fifth period.

In a fifth possible implementation manner, with reference to the thirdpossible implementation manner, the receiver is specifically configuredto:

receive, according to a first frequency domain granularity, the PMI₁sent by the UE; and

receive, according to a second frequency domain granularity, the PMI₂sent by the UE, where the first frequency domain granularity is greaterthan the second frequency domain granularity; or

receive, according to a third frequency domain granularity, the PMI₃sent by the UE; and

receive, according to a fourth frequency domain granularity, the PMI₄sent by the UE, where the third frequency domain granularity is greaterthan the fourth frequency domain granularity; or

receive, according to a second frequency domain granularity, the PMI₂sent by the UE;

receive, according to a third frequency domain granularity, the PMI₃sent by the UE; and

receive, according to a fifth frequency domain granularity, the PMI₅sent by the UE, where the third frequency domain granularity is lessthan the second frequency domain granularity and the fifth frequencydomain granularity.

In a sixth possible implementation manner, with reference to the fourthaspect or the first to fifth possible implementation manners, the blockmatrix X_(i)=[X_(i,1) X_(i,2)], where each column of the matrix x_(i,j)is selected from columns of a Householder matrix, a discrete Fouriertransform matrix, a Hadamard matrix, a rotated Hadamard matrix, or aprecoding matrix in an LTE R8 system 2-antenna or 4-antenna codebook orin an LTE R10 system 8-antenna codebook.

In a seventh possible implementation manner, with reference to the sixthpossible implementation manner, each column of the matrix x_(i,j) isseparately selected from columns of different Householder matrices,different discrete Fourier transform matrices, different Hadamardmatrices, different rotated Hadamard matrices, or different precodingmatrices in an LTE R8 system 2-antenna or 4-antenna codebook or in anLTE R10 system 8-antenna codebook.

In an eighth possible implementation manner, with reference to thefourth aspect or the first to fifth possible implementation manners, theblock matrix X_(i)=[X_(i,1) X_(i,2)], where the matrix x_(i,j) is aKronecker product of two matrices being A_(i,j) and B_(i,j), and j=1, 2.

In a ninth possible implementation manner, with reference to the eighthpossible implementation manner, columns of the matrix X_(i,1) and thematrix X_(i,2) are column vectors of a Householder matrix, a discreteFourier transform matrix, a Hadamard matrix, a rotated Hadamard matrix,or a precoding matrix in an LTE R8 system 2-antenna or 4-antennacodebook or in an LTE R10 system 8-antenna codebook.

In a tenth possible implementation manner, with reference to the fourthaspect or the first to ninth possible implementation manners, w₁ is anidentity matrix.

In an eleventh possible implementation manner, with reference to thefourth aspect or the first to tenth possible implementation manners, acolumn vector in the matrix W₂ has a structure y_(n)=γ⁻¹[e_(n) ^(T)e^(jθ) ^(n) e_(n) ^(T)]^(T), where e_(n) represents a selection vector;where in the vector, the n^(th) element is 1 and all other elements are0; θ_(n) is a phase shift; and γ is a positive constant.

The embodiments of the present invention provide a method for reportingchannel state information, user equipment, and a base station. Themethod includes: after receiving reference information sent by a basestation, selecting, by user equipment based on the referenceinformation, a precoding matrix from a codebook, where a precodingmatrix w included in the codebook is a product of three matrices beingW₁, Z, and W₂, where both W₁ and Z are block diagonal matrices,W₁=diag{X₁, . . . , X_(N) _(B) }, Z=diag{Z₁, . . . , Z_(N) _(B) }, eachof W₁ and Z includes at least one block matrix, that is, N_(B)≥1, andeach column of each block matrix Z_(i) in the matrix Z has the followingstructure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T)

where [ ]^(T) represents matrix transposition; e_(i,k) represents ann_(i)x1 selection vector, where in the vector, the k^(th) element is 1and all other elements are 0, and n_(i) is a half of a column quantityof a block matrix x_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, andβ_(i,k)≥0; and sending a precoding matrix indicator PMI to the basestation according to the selected precoding matrix W, where the PMI isused by the base station to obtain the selected precoding matrix Waccording to the PMI. In the precoding matrix indicated in the channelstate information reported by the user equipment, a channelcharacteristic of a double-transmission condition in a micro cellnetwork environment and freedom in a perpendicular direction of anantenna are considered, which can improve communication performance ofthe micro cell network environment and the freedom in the perpendiculardirection of the antenna.

BRIEF DESCRIPTION OF THE DRAWINGS

To describe the technical solutions in the embodiments of the presentinvention or in the prior art more clearly, the following brieflyintroduces the accompanying drawings required for describing theembodiments or the prior art. Apparently, the accompanying drawings inthe following descriptions show merely some embodiments of the presentinvention, and a person of ordinary skill in the art may still deriveother drawings from these accompanying drawings without creativeefforts.

FIG. 1 is a schematic flowchart of a method for reporting channel stateinformation according to an embodiment of the present invention;

FIG. 2 is a schematic flowchart of another method for reporting channelstate information according to an embodiment of the present invention;

FIG. 3 is a schematic flowchart of still another method for reportingchannel state information according to an embodiment of the presentinvention;

FIG. 4 is a schematic diagram of interaction in a method for reportingchannel state information according to an embodiment of the presentinvention;

FIG. 5 is a schematic structural diagram of user equipment according toan embodiment of the present invention;

FIG. 6 is a schematic structural diagram of another user equipmentaccording to an embodiment of the present invention;

FIG. 7 is a schematic structural diagram of a base station according toan embodiment of the present invention; and

FIG. 8 is a schematic structural diagram of another base stationaccording to an embodiment of the present invention.

DETAILED DESCRIPTION

Various technologies described in this specification are applicable to aLong Term. Evolution (LTE) system. The user equipment may be a wirelessterminal or a wired terminal. The wireless terminal may refer to adevice that provides a user with voice and/or data connectivity, ahandheld device with a radio connection function, or another processingdevice connected to a radio modem. The wireless terminal may communicatewith one or more core networks through a radio access network (RAN). Thewireless terminal may be a mobile terminal, such as a mobile phone (alsoreferred to as a “cellular” phone) and a computer with a mobileterminal, for example, may be a portable, pocket-sized, handheld,computer built-in, or in-vehicle mobile apparatus, which exchanges voiceand/or data with the radio access network. For example, it may be adevice such as a personal communications service (PCS) phone, a cordlesstelephone set, a Session Initiation Protocol (SIP) phone, a wirelesslocal loop (WLL) station, or a personal digital assistant (PDA). Thewireless terminal may also be referred to as a system, a subscriberunit, a subscriber station, a mobile station, a remote station, anaccess point, a remote terminal, an access terminal, a user terminal, auser agent, a user device, user equipment, or a relay, which is notlimited in the present invention.

In addition, the terms “system” and “network” may be usedinterchangeably in this specification. The term “and/or” in thisspecification describes only an association relationship for describingassociated objects and represents that three relationships may exist.For example, A and/or B may represent the following three cases: Only Aexists, both A and B exist, and only B exists. In addition, thecharacter “/” in this specification generally indicates an “or”relationship between the associated objects.

Embodiment 1

This embodiment of the present invention provides a method for reportingchannel state information. The method is executed by user equipment(UE), and as shown in FIG. 1, the method includes:

Step 101: Receive a reference signal sent by a base station.

Specifically, the reference signal sent by the base station may includea channel state information reference signal (CSI RS), or a demodulationreference signal (DM RS), or a cell-specific reference signal (CRS). Theuser equipment UE may obtain a resource configuration of the referencesignal by receiving a notification of the eNB such as RRC (radioresource control) signaling or DCI (downlink control information), or onthe basis of a cell identity (ID); and obtain the reference signal in acorresponding resource or subframe.

Step 102: Select, based on the reference signal, a precoding matrix froma codebook, where a precoding matrix w included in the codebook is aproduct of three matrices being W₁, z, and W₂, that is,w=w ₁ zw ₂  (1)

where both w₁ and z are block diagonal matrices, that is:W ₁=diag{X ₁ , . . . ,X _(N) _(B) }  (2)Z=diag{Z ₁ , . . . ,Z _(N) _(B) }  (3)

and meet the following condition:W ₁ Z=diag{X ₁ Z ₁ , . . . ,X _(N) _(B) Z _(N) _(B) }  (4)

each of W₁ and z includes at least one block matrix, that is, a blockmatrix quantity N_(B)≥1, and each column of each block matrix z_(i) inthe matrix Z has the following structure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T)  (5)

where [ ]^(T) represents matrix transposition; e_(i,k) represents ann_(i)x1 selection vector, where in the vector, the k^(th) element is 1and all other elements are 0, and n_(i) is a half of a column quantityof a block matrix X_(i), that is, 2n_(i) is a column quantity of theblock matrix x_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, β_(i,k)≥0; andX_(i) corresponds to Z_(i).

In the structure (5), for the precoding matrix, two column vectors (orreferred to as beams) can be separately selected from each block matrixx_(i) by using two e_(i,k) and z_(i,k); phase alignment and weightingare performed on the two column vectors (or beams) by using α_(i,k) andβ_(i,k)e^(jθ) ^(i,k) , where the two column vectors selected from X_(i)may separately point to two major multipath transmission directions.

In analysis from the perspective of physical meaning, the block diagonalmatrix W₁ is a beam group formed by the block matrices X_(i) thatinclude different beams (or column vectors), and correspondingly, eachcolumn of each block matrix Z_(i) included in the matrix Z is used tocombine (including phase alignment and weighting) two beams in the blockmatrix X_(i), where directions of the two beams may separately point totwo major multipath transmission directions. Therefore, for each columnof an obtained matrix X_(i)Z_(i) interference between two majormultipath transmission directions can be converted into a wanted signalby using the foregoing structure, thereby significantly improvingtransmit power corresponding to each column of X_(i)Z_(i).

The parameters α_(i,k) and β_(i,k) may be equal, and in this case,equal-power combining gains of two beams are obtained. One of theparameters α_(i,k) and β_(i,k) may be 0, and in this case, selectivecombining gains of two beams are obtained. The parameters α_(i,k) andβ_(i,k) may also be other quantized values, for example, a value ofβ_(i,k)e^(jθ) ^(i,k) may be selected from a constellation diagram ofmodulation such as 16QAM or 64QAM, and in this case, maximum ratiocombining gains of two beams are obtained.

The matrix W₂ is used to select one or more column vectors in the matrixW₁Z and perform weighting combination to form the matrix W. By using thematrix W₂, the precoding matrix W can further adapt to a sub-band or ashort-term characteristic of a channel, and one-layer or multi-layertransmission is formed, thereby improving a transmission rate.

Specifically, the block matrix X_(i) in the matrix W₁ may have thefollowing structure:X _(i)=[X _(i,1) X _(i,2)],1≤i≤N _(B)  (6)

where, each column of the matrix x_(i,j) may be selected from columns ofa Householder (Householder) matrix H, where the matrix H is:H∈{I−2u _(n) u _(n) ^(H) /u _(n) ^(H) u _(n)}  (7)

For example, the vector u_(n) may be a vector used in an LTE R84-antenna codebook, and is shown in the following table:

u₀ = [1 −1 −1 −1]^(T) u₁ = [1 −j 1 j]^(T) u₂ = [1 1 −1 1]^(T) u₃ = [1 j1 −j]^(T) u₄ = [1 (−1 − j)/{square root over (2)} −j (1 − j)/{squareroot over (2)}]^(T) u₅ = [1 (1 − j)/{square root over (2)} j (−1 −j)/{square root over (2)}]^(T) u₆ = [1 (1 + j)/{square root over (2)} −j(−1 + j)/{square root over (2)}]^(T) u₇ = [1 (−1 + j)/{square root over(2)} j (1 + j)/{square root over (2)}]^(T) u₈ = [1 −1 1 1]^(T) u₉ = [1−j −1 −j]^(T) u₁₀ = [1 1 1 −1]^(T) u₁₁ = [1 j −1 j]^(T) u₁₂ = [1 −1 −11]^(T) u₁₃ = [1 −1 1 −1]^(T) u₁₄ = [1 1 −1 −1]^(T) u₁₅ = [1 1 1 1]^(T)

Each column in the two matrices X_(i,j), j=1, 2 may be from a column setof a same Householder matrix H, or may be separately from column sets ofdifferent Householder matrices H. In the former case, columns inX_(i,j), j=1, 2 are orthogonal to each other, and it is suitable formultipath transmission directions that are orthogonal to each other. Inthe latter case, columns in X_(i,j), j=1, 2 may be close to each other,and it is suitable for multipath transmission directions that are notorthogonal to each other.

Each column of the matrix x_(i,j) in formula (6) may also be selectedfrom columns of a discrete Fourier transform (DFT) matrix F, where thematrix F is:

$\begin{matrix}{F \in \left\{ {{F_{g} = \left\lbrack e^{j\frac{2\;\pi\; m}{N}{({n + {g/G}})}} \right\rbrack_{N \times N}},{g = 0},1,{{\ldots\mspace{14mu} G} - 1}} \right\}} & (8)\end{matrix}$

where

$\left\lbrack e^{j\frac{2\;\pi\; m}{N}{({n + \frac{g}{G}})}} \right\rbrack_{N \times N}$represents that an element in the (m+1)^(th) row and the (n+1)^(th)column is an N×N matrix of

$e^{j\frac{2\;\pi\; m}{N}{({n + {g/G}})}},$where

m,n=0, 1 . . . , N−1; j represents a unit pure imaginary number, thatis, j=√{square root over (−1)}; G is a positive integer; and g/G is aphase shift parameter. Multiple different DFT matrices may be obtainedby selecting G and g. Columns of the two matrices x_(i,j), j=1, 2 may befrom a same DFT matrix F, or may be from different DFT matrices F. Inthe former case, columns in x_(i,j), j=1, 2 are orthogonal to eachother, and it is suitable for multipath transmission directions that areorthogonal to each other. In the latter case, columns in x_(i,j), j=1, 2may be close to each other, and it is suitable for multipathtransmission directions that are not orthogonal to each other.

Each column of the matrix x_(i,j) in formula (6) may also be selectedfrom columns of the following Hadamard (Hadamard) matrix or rotatedHadamard matrix:diag{1,e ^(jmπ/N) ,e ^(jmπ/N) ,e ^(j3m/N) }H _(n)  (9)

where N is a positive integer, m=0, . . . , N−1, H_(n) is an n-orderHadamard matrix, and j represents a unit pure imaginary number, that is,j=√{square root over (−1)}. When m=0, a matrix shown in (10) is ann-order Hadamard matrix H_(n). For example, H₄ is:

$\begin{matrix}{H_{4} = \begin{bmatrix}1 & 1 & 1 & 1 \\1 & {- 1} & 1 & {- 1} \\1 & 1 & {- 1} & {- 1} \\1 & {- 1} & {- 1} & 1\end{bmatrix}} & (10)\end{matrix}$

Columns in the two matrices x_(i,j), j=1, 2 may be from a same Hadamardmatrix or rotated Hadamard matrix, or may be from different Hadamardmatrices or rotated Hadamard matrices. In the former case, columns inx_(i,j), j=1, 2 are orthogonal to each other, and it is suitable formultipath transmission directions that are orthogonal to each other. Inthe latter case, columns in x_(i,j), j=1, 2 may be close to each other,and it is suitable for multipath transmission directions that are notorthogonal to each other.

Each column of the matrix x_(i,j) in formula (6) may also be selectedfrom columns of a precoding matrix in an LTE R8 system 2-antenna or4-antenna codebook or in an LTE R10 system 8-antenna codebook. Columnsof the two matrices x_(i,j), j=1, 2 may be from a same precoding matrix,or may be from different precoding matrices. In the former case, columnsin x_(i,j), j=1, 2 are orthogonal to each other, and it is suitable formultipath transmission directions that are orthogonal to each other. Inthe latter case, columns in x_(i,j), j=1, 2 may be close to each other,and it is suitable for multipath transmission directions that are notorthogonal to each other.

The matrix x_(i,j) in formula (6) may also have the following structure:x _(i,j) =A _(i,j) ⊗B _(i,j),1≤i≤N _(B) ,j=1,2  (11)

That is, the block matrix x_(i,j) is a Kronecker (kronecker) product ofa matrix A_(i,j) and a matrix B_(i,j), where j=1, 2.

Further, each column of the matrix A_(i,j) or the matrix B_(i,j) informula (11) may be a column vector of the Householder matrix shown in(7), or the DFT matrix shown in (8), or the Hadamard matrix or therotated Hadamard matrix shown in (9) or (10), or the precoding matrix inthe LTE R8 system 2-antenna or 4-antenna codebook or in the LTE R10system 8-antenna codebook. In addition, other forms may also be used forthe matrix A_(i,j) or the matrix B_(i,j), which are not described indetail herein.

For the matrix A_(i,j) or the matrix B_(i,j) in the structure (11),beamforming and precoding may be separately performed in a horizontaldirection and a perpendicular direction of an AAS base station.Therefore, the precoding matrix w can adapt to an antenna configurationof the AAS base station, thereby fully using freedom in horizontal andperpendicular directions of an antenna of the AAS base station.

Columns in the two matrices being A_(i,j) and B_(i,j) j=1, 2 may be froma same precoding matrix in formula (7) to formula (10) or in the LTE R8system 2-antenna or 4-antenna codebook or in the LTE R10 system8-antenna codebook, or may be from different precoding matrices. In theformer case, columns in x_(i,j), j=1, 2 are orthogonal to each other,and it is suitable for multipath transmission directions that areorthogonal to each other. In the latter case, columns in x_(i,j), j=1, 2may be close to each other, and it is suitable for multipathtransmission directions that are not orthogonal to each other.

Further, the block matrices X_(i) in formula (6) may be equal to eachother, where 1≤i≤N_(B); in this way, relevance between channels can befully used, and feedback overheads can be further reduced.

Specifically, the block matrix X_(i) in the matrix W₁ may also be anidentity matrix, that is, W₁ is an identity matrix; and in this case,w₁z=z. In this case, the structure shown in (5) helps select two antennaports by directly using two e_(i,k) in z_(i,k), and helps perform phasealignment and weighting on the two antenna ports by using α_(i,k)e^(jθ)^(i,k) , where the two selected antenna ports may separately align withtwo major multipath transmission directions. An actually deployedantenna port may correspond to a virtual antenna, where each virtualantenna is obtained by performing weighting combination on multiplephysical antennas, and virtual antennas may have different beamdirections; therefore, in the foregoing precoding structure, differentbeam directions of the antenna ports can be fully used, and interferencebetween two major multipath transmission directions can be directlyconverted into a wanted signal, thereby significantly improving a systemtransmission rate.

Specifically, the phase θ_(i,k) in the structure (5) may be selectedfrom the following values:

$\begin{matrix}{\theta_{i,k} \in \left\{ {0,\frac{2\;\pi}{N},\ldots\mspace{14mu},\frac{\left( {N - 1} \right)2\;\pi}{N}} \right\}} & (12)\end{matrix}$

where N is a positive integer, for example, N is 2 to the power of n,where n is a positive integer.

Further, the foregoing block matrices Z_(i) may be equal to each other,where 1≤i≤N_(B); in this way, relevance between channels can be fullyused, and feedback overheads can be further reduced.

The matrix W₂ is used to select or perform weighting combination on acolumn vector in the matrix w₁z to form the matrix W.

Specifically, a column vector in the matrix w₂ has a structure:y_(n)=γ⁻¹[e_(n) ^(T) e^(jθ) ^(n) e_(n) ^(T)]^(T), where e_(n) representsa selection vector, where in the vector, the n^(th) element is 1 and allother elements are 0; θ_(n) is a phase shift; and β is a positiveconstant.

An example in which a block matrix quantity N_(B)=2 and two blockmatrices x₁z₁ and x₂z₂ in w₁z separately have 4 columns is used, and thematrix w₂ may be:

$\begin{matrix}{\mspace{79mu}{W_{2} \in \left\{ {{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\Y\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\{jY}\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\{- Y}\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\{- {jY}}\end{bmatrix}}} \right\}}} & (13) \\{\mspace{79mu}{Y \in \left\{ {{\overset{\sim}{e}}_{1},{\overset{\sim}{e}}_{2},{\overset{\sim}{e}}_{3},{\overset{\sim}{e}}_{4}} \right\}}} & (14) \\{\mspace{79mu}{or}} & \; \\{\mspace{79mu}{W_{2} \in \left\{ {{\frac{1}{\sqrt{2}}\begin{bmatrix}Y_{1} & Y_{2} \\Y_{1} & {- Y_{2}}\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y_{1} & Y_{2} \\{jY}_{1} & {- {jY}_{2}}\end{bmatrix}}} \right\}}} & (15) \\{\left( {Y_{1},Y_{2}} \right) \in \left\{ {\left( {{\overset{\sim}{e}}_{1},{\overset{\sim}{e}}_{1}} \right),\left( {{\overset{\sim}{e}}_{2},{\overset{\sim}{e}}_{2}} \right),\left( {{\overset{\sim}{e}}_{3},{\overset{\sim}{e}}_{3}} \right),\left( {{\overset{\sim}{e}}_{4},{\overset{\sim}{e}}_{4}} \right),\left( {{\overset{\sim}{e}}_{1},{\overset{\sim}{e}}_{2}} \right),\left( {{\overset{\sim}{e}}_{2},{\overset{\sim}{e}}_{3}} \right),\left( {{\overset{\sim}{e}}_{1},{\overset{\sim}{e}}_{4}} \right),\left( {{\overset{\sim}{e}}_{2},{\overset{\sim}{e}}_{4}} \right)} \right\}} & (16)\end{matrix}$

where {tilde over (e)}_(n), n=1, 2, 3, 4 represents a 4×1 selectionvector, where in the vector, the n^(th) element is 1 and all otherelements are 0.

An example in which a block matrix quantity N_(B)=2, and two blockmatrices x₁z₁ and x₂z₂ in w₁z separately have 8 columns is used, and thematrix w₂ may be:

$\begin{matrix}{\mspace{79mu}{W_{2} \in \left\{ {{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\Y\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\{jY}\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\{- Y}\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\{- {jY}}\end{bmatrix}}} \right\}}} & (17) \\{\mspace{79mu}{Y \in \left\{ {e_{1},e_{2},e_{3},e_{4},e_{5},e_{6},e_{7},e_{8}} \right\}}} & (18) \\{\mspace{79mu}{or}} & \; \\{\mspace{79mu}{W_{2} \in \left\{ {{\frac{1}{\sqrt{2}}\begin{bmatrix}Y_{1} & Y_{2} \\Y_{1} & {- Y_{2}}\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y_{1} & Y_{2} \\{jY}_{1} & {- {jY}_{2}}\end{bmatrix}}} \right\}}} & (19) \\{\left( {Y_{1},Y_{2}} \right) \in \left\{ {\left( {e_{1},e_{1}} \right),\left( {e_{2},e_{2}} \right),\left( {e_{3},e_{3}} \right),\left( {e_{4},e_{4}} \right),\left( {e_{1},e_{2}} \right),\left( {e_{2},e_{3}} \right),\left( {e_{1},e_{4}} \right),\left( {e_{2},e_{4}} \right)} \right\}} & (20)\end{matrix}$

where e_(n), n=1, 2, . . . , 8 represents an 8×1 selection vector, wherein the vector, the n^(th) element is 1 and all other elements are 0.

Specifically, the selecting, based on the reference signal, a precodingmatrix from a codebook may include:

obtaining, by the user equipment UE based on the reference signal,channel estimation, and selecting the precoding matrix from the codebookaccording to the channel estimation and based on a predefined rule suchas a rule of maximizing a channel capacity or a throughput, whereselection, based on a predefined rule, of a precoding matrix is theprior art, and is not described in detail herein.

Step 103: Send a precoding matrix indicator (PMI) to the base stationaccording to the selected precoding matrix w, where the PMI is used bythe base station to obtain the selected precoding matrix w according tothe PMI.

Specifically, the precoding matrix w is included in a precoding matrixset or a codebook, and the PMI is used to indicate the precoding matrixw selected from the precoding matrix set or the codebook.

Specifically, the sending a precoding matrix indicator PMI to the basestation includes: sending the precoding matrix indicator PMI to the basestation, where the PMI may only include a specific value, and in thiscase, the PMI directly indicates the precoding matrix w. For example,there are a total of 16 different precoding matrices, and PMI=0, . . . ,15 may be used to respectively indicate precoding matrices w marked as0, 1, . . . , 15.

Specifically, the sending a precoding matrix indicator PMI to the basestation may also include: sending precoding matrix indicators PMI₁ andPMI₂ to the base station, where the PMI₁ and the PMI₂ are respectivelyused to indicate the matrix w₁z and the matrix W₂ in formula (1), and inthis case, the matrix w₁z and the matrix W₂ are respectively indicatedby the PMI₁ and the PMI₂ in the codebook;

or

the sending a precoding matrix indicator PMI to the base station mayalso include: sending a third precoding matrix indicator PMI₃ and afourth precoding matrix indicator PMI₄ to the base station, where thePMI₃ is used to indicate the matrix W₁, and the PMI₄ is used to indicatethe matrix zw₂;

or

sending a second precoding matrix indicator PMI₂, a third precodingmatrix indicator PMI₃, and a fifth precoding matrix indicator PMI₅ tothe base station, where the PMI5 is used to indicate the matrix z.

Further, the precoding matrix indicators PMI₁ and PMI₂, or PMI₃ andPMI₄, or PMI₂, PMI₃, and PMI₅ have different time domains or frequencydomain granularities. Specifically, the sending a precoding matrixindicator PMI to the base station specifically includes:

sending the PMI₁ to the base station according to a first period; and

sending the PMI₂ to the base station according to a second period, wherethe first period is greater than the second period; or

sending the PMI₃ to the base station according to a third period; and

sending the PMI₄ to the base station according to a fourth period, wherethe third period is greater than the fourth period; or

sending the PMI₂ to the base station according to a second period;

sending the PMI₃ to the base station according to a third period; and

sending the PMI₅ to the base station according to a fifth period, wherethe third period is less than the second period and the fifth period;

or, sending the PMI₁ to the base station according to a first frequencydomain granularity; and

sending the PMI₂ to the base station according to a second frequencydomain granularity, where the first frequency domain granularity isgreater than the second frequency domain granularity, for example,sending a wideband PMI₁ and a sub-band PMI₂ to the base station; or

sending the PMI₃ to the base station according to a third frequencydomain granularity; and

sending the PMI₄ to the base station according to a fourth frequencydomain granularity, where the third frequency domain granularity isgreater than the fourth frequency domain granularity, for example,sending a wideband PMI₃ and a sub-band PMI₄ to the base station; or

sending the PMI₂ to the base station according to a second frequencydomain granularity;

sending the PMI₃ to the base station according to a third frequencydomain granularity; and

sending the PMI₅ to the base station according to a fifth frequencydomain granularity, where the third frequency domain granularity is lessthan the second frequency domain granularity and the fifth frequencydomain granularity, for example, sending a wideband PMI₂, a widebandPMI₅, and a sub-band PMI₃ to the base station.

It should be noted that, the sizes of the foregoing wideband andsub-band may vary with the size of a system bandwidth. For example, in a10 MHz LTE system that includes 50 physical resource blocks (RBs), thewideband may include 50 RBs, and the size of the sub-band may be 6consecutive RBs; and in a 5 MHz LTE system, the wideband may include 25RBs, and the size of the sub-band may be 3 consecutive RBs.

For the foregoing different time domains, or frequency domaingranularities, or reporting periods, feedback overheads can be furtherreduced by using time or frequency domain relevance between channels.

Specifically, the sending a precoding matrix indicator (PMI) to the basestation may also include: sending a precoding matrix indicator PMI1_(i),where 1≤i≤N_(B), and the PMI₂ to the base station; PMI1_(i), where1≤i≤N_(B), and the PMI₂ are respectively used to indicate the matrixx_(i)z_(i), where 1≤i≤N_(B), and the matrix W₂;

or sending a precoding matrix indicator PMI3_(i), where 1≤i≤N_(B), andthe PMI₄ to the base station; PMI3_(i), where 1≤i≤N_(B), is used toindicate X_(i), and the PMI₄ is used to indicate the matrix zw₂;

or sending a precoding matrix indicator PMI3_(i), where 1≤i≤N_(B), thePMI₂, and the PMI₅ to the base station, where the PMI5 is used toindicate the matrix z.

Specifically, the sending a precoding matrix indicator (PMI) to the basestation may also include: sending a precoding matrix indicator PMI5_(i),where 1≤i≤N_(B)/2, and the PMI₂ to the base station; PMI5_(i) where1≤i≤N_(B)/2, and the PMI₂ are respectively used to indicate the matrixx_(2i-1)z_(2i-1)=x_(2i)z_(2i), where 1≤i≤N_(B)/2, and a matrix W₂; andin this case, X_(2i-1)Z_(2i-1)=X_(2i)Z_(2i) and the two matrices appearin pairs.

Specifically, the sending a precoding matrix indicator (PMI) to the basestation may be: sending, by the UE, the precoding matrix indicator PMIto the base station through a physical uplink control channel (PUCCH) ora physical uplink shared channel (PUCCH).

Further, the sending a precoding matrix indicator (PMI) to the basestation may be: separately sending, by the UE to the base station byusing different subframes or in different periods, the PMI₁ and thePMI₂, or the PMI₃ and the PMI₄, or the PMI₂, the PMI₃, and the PMI₃, orthe PMI1_(i), where 1≤i≤N_(B), and the PMI₂, or the PMI3,_(i) and thePMI₄, or the PMI3_(i), where 1≤i≤N_(B), the PMI₂, and the PMI₅, or thePMI5_(i), where 1≤i≤N_(B)/2, and the PMI₂.

Further, the sending a precoding matrix indicator (PMI) to the basestation may also be: separately sending, by the UE to the base stationaccording to different sub-bands or sub-band widths in a frequencydomain, the PMI₁ and the PMI₂, or the PMI₃ and the PMI₄, or the PMI₂,the PMI₃, and the PMI₅, or the PMI1_(i), where 1≤i≤N_(B), and the PMI₂,or the PMI3,_(i) and the PMI₄, or the PMI3_(i), where 1≤i≤N_(B), thePMI₂, and the PMI₅, or the PMI5_(i), where 1≤i≤N_(B)/2, and the PMI₂.

In addition, multiple block matrices X_(i) may separately correspond toantenna groups of different polarizations or different locations;therefore, the precoding matrix can match multiple antenna deploymentsor configurations. The foregoing codebook structure can significantlyimprove performance of MIMO, especially MU-MIMO.

In addition, one or more PMIs are fed back based on a subset, toindicate the precoding matrix; therefore, time/frequency domain/spacerelevance between channels is fully used, thereby significantly reducingfeedback overheads.

Further, as shown in FIG. 2, after the step 201 of receiving a referencesignal sent by a base station, the selecting, based on the referencesignal, a precoding matrix from a codebook is specifically:

202: Select, based on the reference signal, the precoding matrix from acodebook subset.

The codebook subset may be a predefined codebook subset; or may be acodebook subset as follows: the codebook subset is reported by the UE tothe base station eNB, notified by the base station eNB based on a reportof the UE, and then told by the base station to the UE; or may be acodebook subset that is determined and reported by the UE, for example,a recently reported codebook subset.

Further, the codebook subset and another codebook subset share at leastone same matrix subset of the following matrix subsets: subsets of amatrix W₁, a matrix w₁z, a matrix W₂, a matrix zw₂, and a matrix Z.

As described above, the precoding matrix is selected based on thecodebook subset, which can further reduce feedback overheads andimplementation complexity.

Further, the codebook subsets share a same subset of the matrix W₁, orthe matrix w₁z, or the matrix W₂, or the matrix zw₂, or the matrix Z,and therefore, the codebook subsets overlap with each other, which canovercome an edge effect of quantization of channel state information.

Further, in the precoding matrix, the block matrices X_(i) of the blockdiagonal matrix W₁ may be unequal, or may be equal. If the blockdiagonal matrix W₁ has multiple equal block matrices, for example, equalblock matrices may appear in pairs, feedback overheads can be furtherreduced.

It should be noted that, the three matrices W₁, Z, and W₂ included inthe precoding matrix W that is selected, based on the reference signal,from the codebook may further be multiplied by a scale factor, so as toimplement power normalization or power balancing. In addition, apartfrom the precoding matrix having the foregoing structure, the codebookmay further include other precoding matrices, so as to meet requirementsof other scenarios, which is not limited herein.

This embodiment of the present invention provides the method forreporting channel state information. The method includes: afterreceiving reference information sent by a base station, selecting, byuser equipment based on the reference information, a precoding matrixfrom a codebook, where a precoding matrix W included in the codebook isa product of three matrices being W₁, Z, and W₂, where both W₁ and Z areblock diagonal matrices, W₁=diag{X₁, . . . X_(N) _(B) }, Z=diag{Z₁, . .. , Z_(N) _(B) }, each of W₁ and Z includes at least one block matrix,that is, N_(B)≥1, and each column of each block matrix z_(i) in thematrix Z has the following structure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T)

where [ ]^(T) represents matrix transposition; e_(i,k) represents ann_(i)x1 selection vector, where in the vector, the k^(th) element is 1and all other elements are 0, and n_(i) is a half of a column quantityof a block matrix x_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, andβ_(i,k)≥0; and sending a precoding matrix indicator (PMI) to the basestation according to the selected precoding matrix w, where the PMI isused by the base station to obtain the selected precoding matrix waccording to the PMI. In the precoding matrix indicated in the channelstate information reported by the user equipment, a channelcharacteristic of a double-transmission condition in a micro cellnetwork environment and freedom in a perpendicular direction of anantenna are considered, that is, each column of each block matrix z inthe matrix z has a structure: z_(i,k)=(α_(i,k) ²+β_(i,k)²)^(−1/2)[α_(i,k)e_(i,k) ^(T) β_(i,k)e^(jθ) ^(i,k) e_(i,k) ^(T)]^(T).For the precoding matrix, two column vectors (or referred to as beams)can be separately selected from each block matrix X_(i) by using thestructure of the matrix Z; and phase alignment and weighting areperformed on the two column vectors (or beams), where the two columnvectors selected from X_(i) may separately point to two major multipathtransmission directions. Therefore, by using the foregoing structure,for each column of an obtained matrix x_(i)z_(i), interference betweentwo major multipath transmission directions can be converted into awanted signal, and combining gains are obtained, thereby improvingsystem transmission reliability and a system transmission throughput.

Embodiment 2

This embodiment of the present invention further provides a method forreporting channel state information. The method is executed by a basestation, and as shown in FIG. 3, the method includes:

301: Send a reference signal to user equipment UE.

302: Receive a precoding matrix indicator (PMI) sent by the UE.

303: Determine a precoding matrix w in a codebook according to the PMI,where the precoding matrix w is a product of three matrices being W₁, Z,and W₂, that is, W=W₁ZW₂, where

both W₁ and Z are block diagonal matrices, W₁=diag{X₁, . . . , X_(N)_(B) }, Z=diag{Z₁, . . . Z_(N) _(B) }, each of w₁ and Z includes atleast one block matrix, that is, N_(B)≥1, and each column of each blockmatrix z_(i) in the matrix Z has the following structure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T)

where [ ]^(T) represents matrix transposition; e_(i,k) represents ann_(i)x1 selection vector, where in the vector, the k^(th) element is 1and all other elements are 0, and n_(i) is a half of a column quantityof a block matrix x_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, β_(i,k)≥0;and X_(i) corresponds to Z_(i).

It should be noted that, apart from the precoding matrix having theforegoing structure, the codebook may further include other precodingmatrices, so as to meet requirements of other scenarios, which is notlimited herein.

In this embodiment of the present invention, user equipment determinesand sends a precoding matrix indicator (PMI), where the PMI indicates aprecoding matrix, and the precoding matrix has a structure: W=W₁ZW₂,where both W₁ and Z are block diagonal matrices, and each column of eachblock matrix Z_(i) in the matrix Z has a structure: z_(i,k)=(α_(i,k)²+β_(i,k) ²)^(−1/2)[α_(i,k)e_(i,k) ^(T)β_(i,k)e^(jθ) ^(i,k) e_(i,k)^(T)]^(T). For the precoding matrix, two column vectors (or referred toas beams) can be separately selected from each block matrix X_(i) byusing the structure of the matrix Z; and phase alignment and weightingare performed on the two column vectors (or beams), where the two columnvectors selected from X_(i) may separately point to two major multipathtransmission directions. Therefore, by using the foregoing structure,for each column of an obtained matrix x_(i)z_(i), interference betweentwo major multipath transmission directions can be converted into awanted signal, and combining gains are obtained, thereby improvingsystem transmission reliability and a system transmission throughput.

Embodiment 3

Based on the methods for reporting channel state information provided inthe foregoing embodiments, the following describes in detail interactionbetween devices for implementing a method for reporting channel stateinformation provided in this embodiment of the present invention, and asshown in FIG. 4, the method includes:

401: Abase station sends a reference signal to user equipment UE.

402: The user equipment receives the reference signal sent by the basestation.

403: The user equipment selects, based on the reference signal, aprecoding matrix from a codebook, where a precoding matrix w included inthe codebook is a product of three matrices being W₁, Z, and W₂, thatis, W=W₁ZW₂, where

both W₁ and z are block diagonal matrices, w₁=diag{X₁, . . . , X_(N)_(B) }, Z=diag{Z₁, . . . , Z_(N) _(B) }, each of W₁ and z includes atleast one block matrix, that is, N_(B)≥1, and each column of each blockmatrix z_(i) in the matrix Z has the following structure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T)

where [ ]^(T) represents matrix transposition; e_(i,k) represents ann_(i)x1 selection vector, where in the vector, the k^(th) element is 1and all other elements are 0, and n_(i) is a half of a column quantityof a block matrix x_(i); θ_(i,k) is a phase shift, α_(i, k)≥0,β_(i,k)≥0; and X_(i) corresponds to z_(i).

404: The user equipment sends a precoding matrix indicator (PMI) to thebase station, where the PMI corresponds to the selected precodingmatrix, and is used by the base station to obtain the selected precodingmatrix w according to the PMI.

405: The base station receives the precoding matrix indicator (PMI) sentby the UE.

406: Determine the precoding matrix w in the codebook according to thePMI.

In this embodiment of the present invention, user equipment determinesand sends a precoding matrix indicator (PMI), where the PMI indicates aprecoding matrix, and the precoding matrix has a structure: W=W₁ZW₂,where both W₁ and Z are block diagonal matrices, and each column of eachblock matrix z_(i) in the matrix Z has a structure: z_(i,k)=(α_(i,k)²+β_(i,k) ²)^(−1/2)[α_(i,k)e_(i,k) ^(T)β_(i,k)e^(jθ) ^(i,k) e_(i,k)^(T)]^(T). For the precoding matrix, two column vectors (or referred toas beams) can be separately selected from each block matrix X_(i) byusing the foregoing structure; and phase alignment and weighting areperformed on the two column vectors (or beams), where the two columnvectors selected from X_(i) may separately point to two major multipathtransmission directions. Therefore, by using the foregoing structure,for each column of an obtained matrix x_(i)z_(i), interference betweentwo major multipath transmission directions can be converted into awanted signal, and combining gains are obtained, thereby improvingsystem transmission reliability and a system transmission throughput.

Embodiment 4

This embodiment of the present invention provides user equipment. Asshown in FIG. 5, the user equipment includes: a receiving unit 51, aselection unit 52, and a sending unit 53.

The receiving unit 51 is configured to receive a reference signal sentby a base station.

The selection unit 52 is configured to select, based on the referencesignal, a precoding matrix from a codebook, where a precoding matrix wincluded in the codebook is a product of three matrices being W₁, z, andW₂, that is, W=W₁ZW₂, where

both W₁ and Z are block diagonal matrices, W₁=diag{X₁, . . . X_(N) _(B)}, Z=diag{Z₁, . . . , Z_(N) _(B) }, each of W₁ and Z includes at leastone block matrix, that is, N_(B)≥1, and each column of each block matrixz_(i) in the matrix Z has the following structure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T)

where [ ]^(T) represents matrix transposition; e_(i,k) represents ann_(i)x1 selection vector, where in the vector, the k^(th) element is 1and all other elements are 0, and n_(i) is a half of a column quantityof a block matrix X_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, β_(i,k)≥0;and X_(i) corresponds to Z_(i).

The sending unit 53 is configured to send a precoding matrix indicator(PMI) to the base station, where the PMI corresponds to the selectedprecoding matrix, and is used by the base station to obtain the selectedprecoding matrix w according to the PMI.

Optionally, the selection unit 52 is specifically configured to select,based on the reference signal, the precoding matrix from a codebooksubset, where the codebook subset is a subset predefined, or notified bythe base station, or reported by the user equipment.

Preferably, the codebook subsets share at least one same matrix subsetof the following matrix subsets: subsets of a matrix W₁, a matrix w₁z, amatrix W₂, a matrix zw₂, and a matrix Z.

Optionally, the sending unit 53 may be specifically configured to send afirst precoding matrix indicator PMI₁ and a second precoding matrixindicator PMI₂ to the base station, where the PMI₁ is used to indicatethe matrix w₁z, and the PMI₂ is used to indicate the matrix W₂; or

send a third precoding matrix indicator PMI₃ and a fourth precodingmatrix indicator PMI₄ to the base station, where the PMI₃ is used toindicate the matrix W₁, and the PMI₄ is used to indicate the matrix zw₂;or

send a second precoding matrix indicator PMI₂, a third precoding matrixindicator PMI₃, and a fifth precoding matrix indicator PMI₅ to the basestation, where the PMI5 is used to indicate the matrix Z.

Optionally, the sending unit 53 may be specifically configured to sendthe PMI₁ to the base station according to a first period; and

send the PMI₂ to the base station according to a second period, wherethe first period is greater than the second period; or

send the PMI₃ to the base station according to a third period; and

send the PMI₄ to the base station according to a fourth period, wherethe third period is greater than the fourth period; or

send the PMI₂ to the base station according to a second period;

send the PMI₃ to the base station according to a third period; and

send the PMI₅ to the base station according to a fifth period, where thethird period is less than the second period and the fifth period.

The sending unit 53 may further be specifically configured to send thePMI₁ to the base station according to a first frequency domaingranularity; and

send the PMI₂ to the base station according to a second frequency domaingranularity, where the first frequency domain granularity is greaterthan the second frequency domain granularity, for example, send awideband PMI_(i) and a sub-band PMI₂ to the base station; or

send the PMI₃ to the base station according to a third frequency domaingranularity; and

send the PMI₄ to the base station according to a fourth frequency domaingranularity, where the third frequency domain granularity is greaterthan the fourth frequency domain granularity, for example, send awideband PMI₃ and a sub-band PMI₄ to the base station; or

send the PMI₂ to the base station according to a second frequency domaingranularity;

send the PMI₃ to the base station according to a third frequency domaingranularity; and

send the PMI₅ to the base station according to a fifth frequency domaingranularity, where the third frequency domain granularity is less thanthe second frequency domain granularity and the fifth frequency domaingranularity, for example, send a wideband PMI₂, a wideband PMI₅, and asub-band PMI₃ to the base station.

It should be noted that, the sizes of the foregoing wideband andsub-band may vary with the size of a system bandwidth. For example, in a10 MHz LTE system, the wideband may include 50 physical resource blocksRBs, and the size of the sub-band may be 6 consecutive RBs; and in a 5MHz LTE system, the wideband may include 25 RBs, and the size of thesub-band may be 3 consecutive RBs.

Optionally, the block matrix X_(i)=[X_(i,1) X_(i,2)], where each columnof the matrix x_(i,j) is selected from columns of a Householder matrix,a discrete Fourier transform matrix, a Hadamard matrix, a rotatedHadamard matrix, or a precoding matrix in an LTE R8 system 2-antenna or4-antenna codebook or in an LTE R10 system 8-antenna codebook.

Further, each column of the matrix x_(i,j), j=1, 2 is separatelyselected from columns of different Householder matrices, differentdiscrete Fourier transform matrices, different Hadamard matrices,different rotated Hadamard matrices, or different precoding matrices inan LTE R8 system 2-antenna or 4-antenna codebook or in an LTE R10 system8-antenna codebook.

Optionally, the block matrix X_(i)=[X_(i,1) X_(i,2)], where the matrixx_(i,j) is a Kronecker product of two matrices being A_(i,j) andB_(i,j), and j=1, 2.

Further, columns of the matrix X_(i,1) and the matrix x_(i,2) are columnvectors of a Householder matrix, a discrete Fourier transform matrix, aHadamard matrix, a rotated Hadamard matrix, or a precoding matrix in anLTE R8 system 2-antenna or 4-antenna codebook or in an LTE R10 system8-antenna codebook.

Optionally, w₁ is an identity matrix.

Optionally, a column vector in the matrix W₂ has a structure:y_(n)=γ⁻¹[e_(n) ^(T) e^(jθ) ^(n) e_(n) ^(T)]^(T), where e_(n) representsa selection vector, where in the vector, the n^(th) element is 1 and allother elements are 0; θ_(n) is a phase shift; and γ is a positiveconstant.

This embodiment of the present invention further provides userequipment. As shown in FIG. 6, the user equipment includes: atransceiver 601, a memory 602, and a processor 603. Certainly, the userequipment may further include common-purpose components such as anantenna and an input/output apparatus, which is not limited herein inthis embodiment of the present invention.

The memory 602 stores a set of program code, and the processor 603 isconfigured to invoke the program code stored in the memory 602, toperform the following operations: receiving, by using the transceiver601, a reference signal sent by a base station; selecting, based on thereference signal, a precoding matrix from a codebook, where a precodingmatrix w included in the codebook is a product of three matrices beingW₁, z, and W₂, that is, W=W₁ZW₂, where

both w₁ and z are block diagonal matrices, W₁=diag{X₁, . . . , X_(N)_(B) }, Z=diag{Z₁, . . . , Z_(N) _(B) }, each of W₁ and Z includes atleast one block matrix, that is, N_(B)≥1, and each column of each blockmatrix z_(i) in the matrix z has the following structure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T)

where [ ]^(T) represents matrix transposition; e_(i,k) represents ann_(i)x1 selection vector, where in the vector, the k^(th) element is 1and all other elements are 0, and n_(i) is a half of a column quantityof a block matrix x_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, β_(i,k)≥0;and X_(i) corresponds to Z_(i); and sending a precoding matrix indicator(PMI) to the base station by using the transceiver 601, where the PMIcorresponds to the selected precoding matrix, and is used by the basestation to obtain the selected precoding matrix w according to the PMI.

The selecting, based on the reference signal, a precoding matrix from acodebook specifically includes:

selecting, based on the reference signal, the precoding matrix from acodebook subset, where the codebook subset is a subset predefined, ornotified by the base station, or reported by the user equipment.

Optionally, the codebook subsets share at least one same matrix subsetof the following matrix subsets: subsets of a matrix W₁, a matrix w₁z, amatrix W₂, a matrix zw₂, and a matrix Z.

Optionally, the sending a precoding matrix indicator (PMI) to the basestation by using the transceiver 601 specifically includes:

sending a first precoding matrix indicator PMI₁ and a second precodingmatrix indicator PMI₂ to the base station, where the PMI₁ is used toindicate the matrix w₁z, and the PMI₂ is used to indicate the matrix W₂;or

sending a third precoding matrix indicator PMI₃ and a fourth precodingmatrix indicator PMI₄ to the base station, where the PMI₃ is used toindicate the matrix w₁, and the PMI₄ is used to indicate the matrix zw₂;or

sending a second precoding matrix indicator PMI₂, a third precodingmatrix indicator PMI₃, and a fifth precoding matrix indicator PMI₅ tothe base station, where the PMI5 is used to indicate the matrix Z.

Optionally, the sending a precoding matrix indicator PMI to the basestation by using the transceiver 601 specifically includes:

sending the PMI₁ to the base station according to a first period; and

sending the PMI₂ to the base station according to a second period, wherethe first period is greater than the second period; or

sending the PMI₃ to the base station according to a third period; and

sending the PMI₄ to the base station according to a fourth period, wherethe third period is greater than the fourth period; or

sending the PMI₂ to the base station according to a second period;

sending the PMI₃ to the base station according to a third period; and

sending the PMI₅ to the base station according to a fifth period, wherethe third period is less than the second period and the fifth period.

Optionally, the sending a precoding matrix indicator (PMI) to the basestation by using the transceiver 601 specifically includes:

sending the PMI₁ to the base station according to a first frequencydomain granularity; and

sending the PMI₂ to the base station according to a second frequencydomain granularity, where the first frequency domain granularity isgreater than the second frequency domain granularity, for example,sending a wideband PMI₁ and a sub-band PMI₂ to the base station; or

sending the PMI₃ to the base station according to a third frequencydomain granularity; and

sending the PMI₄ to the base station according to a fourth frequencydomain granularity, where the third frequency domain granularity isgreater than the fourth frequency domain granularity, for example,sending a wideband PMI₃ and a sub-band PMI₄ to the base station; or

sending the PMI₂ to the base station according to a second frequencydomain granularity;

sending the PMI₃ to the base station according to a third frequencydomain granularity; and

sending the PMI₅ to the base station according to a fifth frequencydomain granularity, where the third frequency domain granularity is lessthan the second frequency domain granularity and the fifth frequencydomain granularity, for example, sending a wideband PMI₂, a widebandPMI₅, and a sub-band PMI₃ to the base station.

It should be noted that, the sizes of the foregoing wideband andsub-band may vary with the size of a system bandwidth. For example, in a10 MHz LTE system, the wideband may include 50 physical resource blocksRBs, and the size of the sub-band may be 6 consecutive RBs; and in a 5MHz LTE system, the wideband may include 25 RBs, and the size of thesub-band may be 3 consecutive RBs.

Optionally, the block matrix X_(i)=[X_(i,1) X_(i,2)], where each columnof the matrix x_(i,j) is selected from columns of a Householder matrix,a discrete Fourier transform matrix, a Hadamard matrix, a rotatedHadamard matrix, or a precoding matrix in an LTE R8 system 2-antenna or4-antenna codebook or in an LTE R10 system 8-antenna codebook.

Further, each column of the matrix x_(i,j), j=1, 2 is separatelyselected from columns of different Householder matrices, differentdiscrete Fourier transform matrices, different Hadamard matrices,different rotated Hadamard matrices, or different precoding matrices inan LTE R8 system 2-antenna or 4-antenna codebook or in an LTE R10 system8-antenna codebook.

Optionally, the block matrix X_(i)=[X_(i,1) X_(i,2)], where the matrixx_(i,j) is a Kronecker product of two matrices being A_(i,j) andB_(i,j), and j=1, 2.

Further, columns of the matrix X_(i,1) and the matrix x_(i,2) are columnvectors of a Householder matrix, a discrete Fourier transform matrix, aHadamard matrix, a rotated Hadamard matrix, or a precoding matrix in anLTE R8 system 2-antenna or 4-antenna codebook or in an LTE R10 system8-antenna codebook.

Optionally, w₁ is an identity matrix.

Optionally, a column vector in the matrix w₂ has a structure:y_(n)=γ⁻¹[e_(n) ^(T) e^(jθ) ^(n) e_(n) ^(T)]^(T), where e_(n) representsa selection vector, where in the vector, the n^(th) element is 1 and allother elements are 0; θ_(n) is a phase shift; and γ is a positiveconstant.

It should be noted that, apart from the precoding matrix having theforegoing structure, the codebook may further include other precodingmatrices, so as to meet requirements of other scenarios, which is notlimited herein.

In this embodiment of the present invention, user equipment determinesand sends a precoding matrix indicator (PMI), where the PMI indicates aprecoding matrix, and the precoding matrix has a structure: W=W₁ZW₂,where both W₁ and Z are block diagonal matrices, and each column of eachblock matrix z_(i) in the matrix Z has a structure: z_(i,k)=(α_(i,k)²+β_(i,k) ²)^(−1/2)[α_(i,k)e_(i,k) ^(T)β_(i,k)e^(jθ) ^(i,k) e_(i,k)^(T)]^(T). For the precoding matrix, two column vectors (or referred toas beams) can be separately selected from each block matrix x_(i) byusing the foregoing structure; and phase alignment and weighting areperformed on the two column vectors (or beams), where the two columnvectors selected from x_(i) may separately point to two major multipathtransmission directions. Therefore, by using the foregoing structure,for each column of an obtained matrix x_(i)z_(i), interference betweentwo major multipath transmission directions can be converted into awanted signal, and combining gains are obtained, thereby improvingsystem transmission reliability and a system transmission throughput.

Embodiment 5

This embodiment of the present invention provides a base station. Asshown in FIG. 7, the base station includes: a sending unit 71, areceiving unit 72, and a determining unit 73.

The sending unit 71 is configured to send a reference signal to userequipment UE.

The receiving unit 72 is configured to receive a precoding matrixindicator (PMI) sent by the UE.

The determining unit 73 is configured to determine a precoding matrix win a codebook according to the PMI, where the precoding matrix w is aproduct of three matrices being W₁, Z, and W₂, that is, W=W₁ZW₂, where

both w₁ and z are block diagonal matrices, W₁=diag{X₁, . . . , X_(N)_(B) }, Z=diag{Z₁, . . . , Z_(N) _(B) }, each of W₁ and z includes atleast one block matrix, that is, N_(B)≥1 and each column of each blockmatrix z_(i) in the matrix Z has the following structure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T)

where [ ]^(T) represents matrix transposition; e_(i,k) represents ann_(i)x1 selection vector, where in the vector, the k^(th) element is 1and all other elements are 0, and n_(i) is a half of a column quantityof a block matrix X_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, β_(i,k)≥0;and X_(i) corresponds to z_(i).

Optionally, the determining unit 73 is specifically configured todetermine the precoding matrix in a codebook subset according to thePMI, where the codebook subset is a subset predefined, or reported bythe user equipment, or notified by the base station.

The codebook subsets share at least one same matrix subset of thefollowing matrix subsets: subsets of a matrix W₁, a matrix w₁z, a matrixW₂, a matrix zw₂, and a matrix Z.

Optionally, the receiving unit 72 is specifically configured to:

receive a first precoding matrix indicator PMI₁ and a second precodingmatrix indicator PMI₂ that are sent by the UE, where the PMI₁ is used toindicate the matrix w₁z, and the PMI₂ is used to indicate the matrix W₂;

or

receive a third precoding matrix indicator PMI₃ and a fourth precodingmatrix indicator PMI₄ that are sent by the UE, where the PMI₃ is used toindicate the matrix W₁, and the PMI₄ is used to indicate the matrix zw₂;

or

receive a second precoding matrix indicator PMI₂, a third precodingmatrix indicator PMI₃, and a fifth precoding matrix indicator PMI₅ thatare sent by the UE, where the PMI5 is used to indicate the matrix z.

Optionally, the receiving unit 72 is specifically configured to:

receive, according to a first period, the PMI₁ sent by the UE; and

receive, according to a second period, the PMI₂ sent by the UE, wherethe first period is greater than the second period; or

receive, according to a third period, the PMI₃ sent by the UE; and

receive, according to a fourth period, the PMI₄ sent by the UE, wherethe third period is greater than the fourth period; or

receive, according to a second period, the PMI₂ sent by the UE;

receive, according to a third period, the PMI₃ sent by the UE; and

receive, according to a fifth period, the PMI₅ sent by the UE, where thethird period is less than the second period and the fifth period.

Optionally, the receiving unit 72 is specifically configured to:

receive, according to a first frequency domain granularity, the PMI₁sent by the UE; and

receive, according to a second frequency domain granularity, the PMI₂sent by the UE, where the first frequency domain granularity is greaterthan the second frequency domain granularity, for example, a widebandPMI₁ and a sub-band PMI₂ are sent to the base station; or

receive, according to a third frequency domain granularity, the PMI₃sent by the UE; and

receive, according to a fourth frequency domain granularity, the PMI₄sent by the UE, where the third frequency domain granularity is greaterthan the fourth frequency domain granularity, for example, a widebandPMI₃ and a sub-band PMI₄ are sent to the base station; or

receive, according to a second frequency domain granularity, the PMI₂sent by the UE;

receive, according to a third frequency domain granularity, the PMI₃sent by the UE; and

receive, according to a fifth frequency domain granularity, the PMI₅sent by the UE, where the third frequency domain granularity is lessthan the second frequency domain granularity and the fifth frequencydomain granularity, for example, a wideband PMI₂, a wideband PMI₅, and asub-band PMI₃ are sent to the base station.

It should be noted that, the sizes of the foregoing wideband andsub-band may vary with the size of a system bandwidth. For example, in a10 MHz LTE system, the wideband may include 50 physical resource blocksRBs, and the size of the sub-band may be 6 consecutive RBs; and in a 5MHz LTE system, the wideband may include 25 RBs, and the size of thesub-band may be 3 consecutive RBs.

Optionally, the block matrix X_(i)=[X_(i,1) X_(i,2)], where each columnof the matrix x_(i,j) is selected from columns of a Householder matrix,a discrete Fourier transform matrix, a Hadamard matrix, a rotatedHadamard matrix, or a precoding matrix in an LTE R8 system 2-antenna or4-antenna codebook or in an LTE R10 system 8-antenna codebook.

Further, each column of the matrix x_(i,j) is separately selected fromcolumns of different Householder matrices, different discrete Fouriertransform matrices, different Hadamard matrices, different rotatedHadamard matrices, or different precoding matrices in an LTE R8 system2-antenna or 4-antenna codebook or in an LTE R10 system 8-antennacodebook.

Optionally, the block matrix X_(i)=[X_(i,1) X_(i,2)], where the matrixx_(i,j) is a Kronecker product of two matrices being A_(i,j) andB_(i,j), and J=1, 2.

Specifically, columns of the matrix X_(i,1) and the matrix x_(i,2) arecolumn vectors of a Householder matrix, a discrete Fourier transformmatrix, a Hadamard matrix, a rotated Hadamard matrix, or a precodingmatrix in an LTE R8 system 2-antenna or 4-antenna codebook or in an LTER10 system 8-antenna codebook.

Optionally, W₁ is an identity matrix.

Optionally, a column vector in the matrix W₂ has a structure:y_(n)=γ⁻¹[e_(n) ^(T) e^(jθ) ^(n) e_(n) ^(T)]^(T), where e_(n) representsa selection vector, where in the vector, the n^(th) element is 1 and allother elements are 0; θ_(n) is a phase shift; and γ is a positiveconstant.

This embodiment of the present invention further provides a basestation. As shown in FIG. 8, the base station includes: a transceiver801, a memory 802, and a processor 803. Certainly, the base station mayfurther include common-purpose components such as an antenna and aninput/output apparatus, which is not limited herein in this embodimentof the present invention.

The memory 802 stores a set of program code, and the processor 803 isconfigured to invoke the program code stored in the memory 802, toperform the following operations:

sending a reference signal to user equipment UE by using the transceiver801; when the user equipment reports a PMI, receiving, by using thetransceiver 801, the precoding matrix indicator (PMI) sent by the UE;and determining a precoding matrix W in a codebook according to the PMI,where the precoding matrix w is a product of three matrices being W₁, zand W₂, that is, W=W₁ZW₂, where

both w₁ and z are block diagonal matrices, W₁=diag{X₁, . . . , X_(N)_(B) }, Z=diag{Z₁, . . . , Z_(N) _(B) }, each of W₁ and Z includes atleast one block matrix, that is, N_(B)≥1, and each column of each blockmatrix z_(i) in the matrix Z has the following structure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T)

where [ ]^(T) represents matrix transposition; e_(i,k) represents ann_(i)x1 selection vector, where in the vector, the k^(th) element is 1and all other elements are 0, and n_(i) is a half of a column quantityof a block matrix x_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, β_(i,k)≥0;and x_(i) corresponds to z_(i).

The determining a precoding matrix w in a codebook according to the PMIspecifically includes: determining the precoding matrix in a codebooksubset according to the PMI, where the codebook subset is a subsetpredefined, or reported by the user equipment, or notified by the basestation.

The codebook subsets share at least one same matrix subset of thefollowing matrix subsets: subsets of a matrix W₁, a matrix w₁z, a matrixW₂, a matrix ZW₂, and a matrix Z.

The receiving the PMI by using the transceiver 801 may specificallyinclude: receiving a first precoding matrix indicator PMI₁ and a secondprecoding matrix indicator PMI₂ that are sent by the UE, where the PMI₁is used to indicate the matrix w₁z, and the PMI₂ is used to indicate thematrix W₂;

or

receiving a third precoding matrix indicator PMI₃ and a fourth precodingmatrix indicator PMI₄ that are sent by the UE, where the PMI₃ is used toindicate the matrix w₁, and the PMI₄ is used to indicate the matrix zw₂;

or

receiving a second precoding matrix indicator PMI₂, a third precodingmatrix indicator PMI₃, and a fifth precoding matrix indicator PMI₅ thatare sent by the UE, where the PMI5 is used to indicate the matrix Z.

The receiving the PMI by using the transceiver 801 may specificallyinclude: receiving, according to a first period, the PMI₁ sent by theUE; and

receiving, according to a second period, the PMI₂ sent by the UE, wherethe first period is greater than the second period; or

receiving, according to a third period, the PMI₃ sent by the UE; and

receiving, according to a fourth period, the PMI₄ sent by the UE, wherethe third period is greater than the fourth period; or

receiving, according to a second period, the PMI₂ sent by the UE;

receiving, according to a third period, the PMI₃ sent by the UE; and

receiving, according to a fifth period, the PMI₅ sent by the UE, wherethe third period is less than the second period and the fifth period.

The receiving the PMI by using the transceiver 801 may furtherspecifically include: receiving, according to a first frequency domaingranularity, the PMI₁ sent by the UE; and

receiving, according to a second frequency domain granularity, the PMI₂sent by the UE, where the first frequency domain granularity is greaterthan the second frequency domain granularity, for example, receiving awideband PMI₁ and a sub-band PMI₂ that are sent by the UE; or

receiving, according to a third frequency domain granularity, the PMI₃sent by the UE; and

receiving, according to a fourth frequency domain granularity, the PMI₄sent by the UE, where the third frequency domain granularity is greaterthan the fourth frequency domain granularity, for example, receiving awideband PMI₃ and a sub-band PMI₄ that are sent by the UE; or

receiving, according to a second frequency domain granularity, the PMI₂sent by the UE;

receiving, according to a third frequency domain granularity, the PMI₃sent by the UE; and

receiving, according to a fifth frequency domain granularity, the PMI₅sent by the UE, where the third frequency domain granularity is lessthan the second frequency domain granularity and the fifth frequencydomain granularity, for example, receiving a wideband PMI₂, a widebandPMI₅, and a sub-band PMI₃ that are sent by the UE.

It should be noted that, the sizes of the foregoing wideband andsub-band may vary with the size of a system bandwidth. For example, in a10 MHz LTE system, the wideband may include 50 physical resource blocksRBs, and the size of the sub-band may be 6 consecutive RBs; and in a 5MHz LTE system, the wideband may include 25 RBs, and the size of thesub-band may be 3 consecutive RBs.

The block matrix X_(i)=[X_(i,1) X_(i,2)], where each column of thematrix x_(i,j) is selected from columns of a Householder matrix, adiscrete Fourier transform matrix, a Hadamard matrix, a rotated Hadamardmatrix, or a precoding matrix in an LTE R8 system 2-antenna or 4-antennacodebook or in an LTE R10 system 8-antenna codebook.

Further, each column of the matrix x_(i,j) is separately selected fromcolumns of different Householder matrices, different discrete Fouriertransform matrices, different Hadamard matrices, different rotatedHadamard matrices, or different precoding matrices in an LTE R8 system2-antenna or 4-antenna codebook or in an LTE R10 system 8-antennacodebook.

Optionally, the block matrix X_(i)=[X_(i,1) X_(i,2)], where the matrixx_(i,j) is a Kronecker product of two matrices being A_(i,j) andB_(i,j), and j=1, 2.

Specifically, columns of the matrix X_(i,1) and the matrix x_(i,2) arecolumn vectors of a Householder matrix, a discrete Fourier transformmatrix, a Hadamard matrix, a rotated Hadamard matrix, or a precodingmatrix in an LTE R8 system 2-antenna or 4-antenna codebook or in an LTER10 system 8-antenna codebook.

Optionally, W₁ is an identity matrix.

Optionally, a column vector in the matrix W₂ has a structure:y_(n)=γ⁻¹[e_(n) ^(T) e^(jθ) ^(n) e_(n) ^(T)]^(T), where e_(n) representsa selection vector, where in the vector, the n^(th) element is 1 and allother elements are 0; θ_(n) is a phase shift; and γ is a positiveconstant.

It should be noted that, apart from the precoding matrix having theforegoing structure, the codebook may further include other precodingmatrices, so as to meet requirements of other scenarios, which is notlimited herein.

In this embodiment of the present invention, after receiving a precodingmatrix indicator (PMI) reported by user equipment, abase stationdetermines a precoding matrix according to the PMI, where the precodingmatrix has a structure: W=W₁ZW₂, where both W₁ and Z are block diagonalmatrices, and each column of each block matrix Z_(i) in the matrix Z hasa structure: z_(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k)e_(i,k)^(T)β_(i,k)e^(jθ) ^(i,k) e_(i,k) ^(T)]^(T). For the precoding matrix,two column vectors (or referred to as beams) can be separately selectedfrom each block matrix X_(i) by using the foregoing structure; and phasealignment and weighting are performed on the two column vectors (orbeams), where the two column vectors selected from X_(i) may separatelypoint to two major multipath transmission directions. Therefore, byusing the foregoing structure, for each column of an obtained matrixx_(i)z_(i), interference between two major multipath transmissiondirections can be converted into a wanted signal, and combining gainsare obtained, thereby improving system transmission reliability and asystem transmission throughput.

It should be noted that, for specific descriptions of some functionmodules in the base station and the user equipment that are provided inthe embodiments of the present invention, reference may be made tocorresponding content in the method embodiments, and details are notdescribed again in this embodiment.

As seen from the descriptions of the foregoing embodiments, it may beclearly understood by a person skilled in the art that, for the purposeof convenient and brief description, division of the foregoing functionmodules is used as an example for illustration. In actual application,the foregoing functions can be allocated to different function modulesand implemented according to a requirement, that is, an inner structureof an apparatus is divided into different function modules to implementall or some of the functions described above. For a detailed workingprocess of the foregoing system, apparatus, and unit, reference may bemade to a corresponding process in the foregoing method embodiments, anddetails are not described herein again.

In the several embodiments provided in the present application, itshould be understood that the disclosed system, apparatus, and methodmay be implemented in other manners. For example, the describedapparatus embodiment is merely exemplary. For example, the module orunit division is merely logical function division and may be otherdivision in actual implementation. For example, a plurality of units orcomponents may be combined or integrated into another system, or somefeatures may be ignored or not performed. In addition, the displayed ordiscussed mutual couplings or direct couplings or communicationconnections may be implemented through some interfaces. The indirectcouplings or communication connections between the apparatuses or unitsmay be implemented in electronic, mechanical, or other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on a plurality ofnetwork units. Some or all of the units may be selected according toactual needs to achieve the objectives of the solutions of theembodiments.

In addition, functional units in the embodiments of the presentinvention may be integrated into one processing unit, or each of theunits may exist alone physically, or two or more units are integratedinto one unit. The integrated unit may be implemented in a form ofhardware, or may be implemented in a form of a software functional unit.

When the integrated unit is implemented in the form of a softwarefunctional unit and sold or used as an independent product, theintegrated unit may be stored in a computer-readable storage medium.Based on such an understanding, the technical solutions of the presentinvention essentially, or the part contributing to the prior art, or allor some of the technical solutions may be implemented in the form of asoftware product. The software product is stored in a storage medium andincludes several instructions for instructing a computer device (whichmay be a personal computer, a server, or a network device) or aprocessor to perform all or some of the steps of the methods describedin the embodiments of the present invention. The foregoing storagemedium includes: any medium that can store program code, such as a USBflash drive, a removable hard disk, a read-only memory (ROM), a randomaccess memory (RAM), a magnetic disk, or an optical disc.

The foregoing descriptions are merely specific implementation manners ofthe present invention, but are not intended to limit the protectionscope of the present invention. Any variation or replacement readilyfigured out by a person skilled in the art within the technical scopedisclosed in the present invention shall fall within the protectionscope of the present invention. Therefore, the protection scope of thepresent invention shall be subject to the protection scope of theclaims.

What is claimed is:
 1. A non-transitory computer-readable storage mediumcomprising instructions which, when executed by a computer, cause thecomputer to: receive a reference signal sent by a base station; select,based on the reference signal, a precoding matrix from a codebook,wherein a precoding matrix W comprised in the codebook is a product ofthree matrices W₁, Z, and W₂, wherein W=W₁ZW₂, both W₁ and Z are blockdiagonal matrices, W₁={X₁, X₂}, Z=diag{Z₁, Z₂}, and each column of eachblock matrix Z_(i) in the matrix Z has the following structure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T) wherein i is an index variable of theblock matrix Z_(i); k is an index variable of the column z_(i,k); []^(T) denotes matrix transpose; e_(i,k) denotes an n_(i)x1 selectionvector, wherein in the vector, the k^(th) element is 1 and all otherelements are 0, and n_(i) is a half of the number of columns of a matrixX_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, and β_(i,k)≥0; W₂ is used toselect one or more column vectors in the matrix W₁Z and to performweighting combination to form the matrix W; and send a precoding matrixindicator (PMI) that corresponds to the selected precoding matrix to thebase station for obtaining the selected precoding matrix W according tothe PMI.
 2. The non-transitory computer-readable storage mediumaccording to claim 1, wherein the matrix X₁ and the matrix X₂ areequivalent.
 3. The non-transitory computer-readable storage mediumaccording to claim 1, wherein the matrix Z₁ and the matrix Z₂ areequivalent.
 4. The non-transitory computer-readable storage mediumaccording to claim 1, wherein the matrix W₁ satisfies at least one ofthe following: X₁=[X_(1,1),X_(1,2)], wherein each column of the matrixX_(1,1) and each column of the matrix X_(1,2) are orthogonal to eachother; or X₂=[X_(2,1), X_(2,2)] wherein each column of the matrixX_(2,1) and each column of the matrix X_(2,2) are orthogonal to eachother.
 5. The non-transitory computer-readable storage medium accordingto claim 1, wherein the matrix W₁ satisfies at least one of thefollowing: X₁=[X_(1,1), X_(1,2)], wherein the matrix X_(1,1) is aKronecker product of matrices A_(1,1) and B_(1,1), and X_(1,2) is aKronecker product of matrices A_(1,2) and B_(1,2), wherein each columnof the A_(1,1), the B_(1,1), the A_(1,2), and the B_(1,2) is a DFTvector; or X₁=[X_(2,1), X_(2,2)], wherein the matrix X_(2,1) is aKronecker product of matrices A_(2,1) and B_(2,1), and X_(1,2) is aKronecker product of matrices A_(2,2) and B_(2,2) wherein each column ofthe A_(2,1), the B_(2,1), the A_(2,2), and the B_(2,2) is a DFT vector.6. The non-transitory computer-readable storage medium according toclaim 1, wherein to send the precoding matrix indicator (PMI) to thebase station, the instructions, when executed by the computer, cause thecomputer to: send a first PMI₁ to the base station for indicating thematrix W₁Z; and send a second PMI, to the base station for indicatingthe matrix W₂.
 7. The non-transitory computer-readable storage mediumaccording to claim 1, wherein: the matrix W₂ is used for columnselection from W₁Z₁ to form the matrix W; or the matrix W₂ is used forweighted combination of the columns of W₁Z₁ to form the matrix W.
 8. Anon-transitory computer-readable storage medium comprising instructionswhich, when executed by a computer, cause the computer to: send areference signal to a terminal; receive precoding matrix indicator (PMI)sent by the terminal; and determine a precoding matrix W in a codebookaccording to the PMI, wherein the precoding matrix W is a product ofthree matrices W₁, Z, and W₂, W=W₁ZW₂, both W₁ and Z are block diagonalmatrices, W₁=diag {X₁, X₂}, Z=diag{Z₁, Z₂}, and each column of eachblock matrix z_(i) in the matrix Z has the following structure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T) wherein i is an index variable of theblock matrix Z_(i); k is an index variable of the column z_(i,k); []^(T) denotes matrix transpose; e_(i,k) denotes an n_(i)x1 selectionvector, wherein in the vector, the k^(th) element is 1 and all otherelements are 0, and n_(i) is a half of the number of columns of a matrixX_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, and β_(i,k)≥0; W₂ is used toselect one or more column vectors in the matrix W₁Z and to performweighting combination to form the matrix W.
 9. The non-transitorycomputer-readable storage medium according to claim 8, wherein thematrix X₁ and the matrix X₂ are equivalent.
 10. The non-transitorycomputer-readable storage medium according to claim 8, wherein thematrix Z₁ and the matrix Z₂ are equivalent.
 11. The non-transitorycomputer-readable storage medium according to claim 8, wherein thematrix W₁ satisfies at least one of the following: X₁=[X_(1,1),X_(1,2)],wherein each column of the matrix X_(1,1) and each column of the matrixX_(1,2) are orthogonal to each other; or X₂=[X_(2,1), X_(2,2)] whereineach column of the matrix X_(2,1) and each column of the matrix X_(2,2)are orthogonal to each other.
 12. The non-transitory computer-readablestorage medium according to claim 8, wherein the matrix W₁ satisfies atleast one of the following: X₁=[X_(1,1),X_(1,2)], wherein the matrixX_(1,1) is a Kronecker product of matrices A_(1,1) and B_(1,1), andX_(1,2) is a Kronecker product of matrices A_(1,2) and B_(1,2), whereineach column of the A_(1,1), the B_(1,1), the A_(1,2), and the B_(1,2) isa DFT vector; or X₁=[X_(2,1), X_(2,2)], wherein the matrix X_(2,1) is aKronecker product of matrices A_(2,1) and B_(2,1), and X_(1,2) is aKronecker product of matrices A_(2,2) and B_(2,2), wherein each columnof the A_(2,1), the B_(2,1), the A_(2,2), and the B_(2,2) is a DFTvector.
 13. The non-transitory computer-readable storage mediumaccording to claim 8, wherein to receive the PMI sent by the terminal,the instructions, when executed by the computer, cause the computer to:receive a first PMI₁ and a second PMI₂ sent by the terminal, wherein thePMI₁ is used to indicate the matrix W₁Z, and the PMI₂ is used toindicate the matrix W₂.
 14. The non-transitory computer-readable storagemedium according to claim 8, wherein: the matrix W₂ is used for columnselection from W₁Z₁ to form the matrix W; or the matrix W₂ is used forweighted combination of the columns of W₁Z₁ to form the matrix W.
 15. Anapparatus for reporting channel state information, comprising: a storagemedium including executable instructions; and a processor; wherein theexecutable instructions, when executed by the processor, cause theapparatus to: receive a reference signal sent by a base station; select,based on the reference signal, a precoding matrix from a codebook,wherein a precoding matrix W comprised in the codebook is a product ofthree matrices W₁, Z, and W₂, wherein W=W₁ZW₂, both W₁ and Z are blockdiagonal matrices, w₁=diag Z=diag{X₁, X₂}, Z=diag{Z₁, Z₂}, and eachcolumn of each block matrix Z_(i) in the matrix Z has the followingstructure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T) wherein i is an index variable of theblock matrix Z_(i); k is an index variable of the column z_(i,k); []^(T) denotes matrix transpose; e_(i,k) denotes an n_(i)x1 selectionvector, wherein in the vector, the k^(th) element is 1 and all otherelements are 0, and n_(i) is a half of the number of columns of a matrixX_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, and β_(i,k)≥0, W₂ is used toselect one or more column vectors in the matrix W₁Z and to performweighting combination to form the matrix W; and send a precoding matrixindicator (PMI) that corresponds to the selected precoding matrix to thebase station for obtaining the selected precoding matrix W according tothe PMI.
 16. The apparatus according to claim 15, wherein the matrix X₁and the matrix X₂ are equivalent.
 17. The apparatus according to claim15, wherein the matrix Z₁ and the matrix Z₂ are equivalent.
 18. Theapparatus according to claim 15, wherein the matrix W₁ satisfies atleast one of the following: X₁=[X_(1,1), X_(1,2)], wherein each columnof the matrix X_(1,1) and each column of the matrix X_(1,2) areorthogonal to each other; or X₂=[X_(2,1), X_(2,2)] wherein each columnof the matrix X_(2,1) and each column of the matrix X_(2,2) areorthogonal to each other.
 19. The apparatus according to claim 15,wherein the matrix W₁ satisfies at least one of the following:X₁=[X_(1,1), X_(1,2)], wherein the matrix X_(1,1) is a Kronecker productof matrices A_(1,1) and B_(1,1), and X_(1,2) is a Kronecker product ofmatrices A_(1,2) and B_(1,2), wherein each column of the A_(1,1), theB_(1,1), the A_(1,2), and the B_(1,2) is a DFT vector; or X₁=[X_(2,1),X_(2,2)], wherein the matrix X_(2,1) is a Kronecker product of matricesA_(2,1) and B_(2,1), and X_(1,2) is a Kronecker product of matricesA_(2,2) and B_(2,2) wherein each column of the A_(2,1), the B_(2,1), theA_(2,2), and the B_(2,2) is a DFT vector.
 20. The apparatus according toclaim 15, wherein to send the precoding matrix indicator (PMI) to thebase station, the instructions, when executed by the processor, causethe processor to: send a first PMI₁ to the base station for indicatingthe matrix W₁Z; and send a second PMI₂ to the base station forindicating the matrix W₂.
 21. The apparatus according to claim 15,wherein: the matrix W₂ is used for column selection from W₁Z₁ to formthe matrix W; or the matrix W₂ is used for weighted combination of thecolumns of W₁Z₁ to form the matrix W.
 22. An apparatus for reportingchannel state information, comprising: a storage medium includingexecutable instructions; and a processor; wherein the executableinstructions, when executed by the processor, cause the apparatus to:send a reference signal to a terminal; receive precoding matrixindicator (PMI) sent by the terminal; and determine a precoding matrix Win a codebook according to the PMI, wherein the precoding matrix W is aproduct of three matrices W₁, Z, and W₂, W=W₁ZW₂, both W₁ and Z areblock diagonal matrices, W₁=diag {X₁,X₂}, Z=diag{Z₁, Z₂}, and eachcolumn of each block matrix Z_(i) in the matrix Z has the followingstructure:z _(i,k)=(α_(i,k) ²+β_(i,k) ²)^(−1/2)[α_(i,k) e _(i,k) ^(T)β_(i,k) e^(jθ) ^(i,k) e _(i,k) ^(T)]^(T) wherein i is an index variable of theblock matrix Z_(i); k is an index variable of the column z_(i,k); []^(T) denotes matrix transpose; e_(i,k) denotes an n_(i)x1 selectionvector, wherein in the vector, the k^(th) element is 1 and all otherelements are 0, and n_(i) is a half of the number of columns of a matrixX_(i); θ_(i,k) is a phase shift, α_(i,k)≥0, and β_(i,k)≥0; W₂ is used toselect one or more column vectors in the matrix W₁Z and to performweighting combination to form the matrix W.
 23. The apparatus accordingto claim 22, wherein the matrix X₁ and the matrix X₂ are equivalent. 24.The apparatus according to claim 22, wherein the matrix Z₁ and thematrix Z₂ are equivalent.
 25. The apparatus according to claim 22,wherein the matrix W₁ satisfies at least one of the following:X₁=[X_(1,1), X_(1,2)], wherein each column of the matrix X_(1,1) andeach column of the matrix X_(1,2) are orthogonal to each other; orX₂=[X_(2,1), X_(2,2)] wherein each column of the matrix X_(2,1) and eachcolumn of the matrix X_(2,2) are orthogonal to each other.
 26. Theapparatus according to claim 22, wherein the matrix W₁ satisfies atleast one of the following: X₁=[X_(1,1), X_(1,2)], wherein the matrixX_(1,1) is a Kronecker product of matrices A_(1,1) and B_(1,1), andX_(1,2) is a Kronecker product of matrices A_(1,2) and B_(1,2), whereineach column of the A_(1,1), the B_(1,1), the A_(1,2), and the B_(1,2) isa DFT vector; or X₁=[X_(2,1), X_(2,2)], wherein the matrix X_(2,1) is aKronecker product of matrices A_(2,1) and B_(2,1), and X_(1,2) is aKronecker product of matrices A_(2,2) and B_(2,2), wherein each columnof the A_(2,1), the B_(2,1), the A_(2,2), and the B_(2,2) is a DFTvector.
 27. The apparatus according to claim 22, wherein to receive thePMI sent by the terminal, the instructions, when executed by theprocessor, cause the processor to: receive a first PMI₁ and a secondPMI₂ sent by the teiininal, wherein the PMI₁ is used to indicate thematrix W₁Z, and the PMI₂ is used to indicate the matrix W₂.
 28. Theapparatus according to claim 22, wherein: the matrix W₂ is used forcolumn selection from W₁Z₁ to form the matrix W; or the matrix W₂ isused for weighted combination of the columns of W₁Z₁ to form the matrixW.